Lava Cakes
Sweet Potato & Oatmeal Caramel Lava Cake
In my mind, every fall dessert is better with oats. Oatmeal cookies are cozy and underrated, and oatmeal cookie dough is even better. If I can add that chewy oat texture and sweet, buttery flavor to a cake, I will.
Here, the oatmeal caramel settles between soft sweet potato cake layers with brown sugar buttercream, while vanilla bean glaze soaks into the warm cakes and spills over the finished top.
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Thinking out loud
The Fall Combination I Found Later
Pumpkin, sweet potato, and apple spice are the obvious fall flavors, but oats belong in that conversation too. They bring a cozy chew that makes a fall dessert feel even more complete.
Sweet potato desserts came to me much later in life. I started baking them in my early 30s. Before that, I had only heard of sweet potato casserole, and we never had it at Thanksgiving because my mom thought it was gross.
Then I learned that sweet potato casserole is one of my favorite Thanksgiving dishes, right next to green bean casserole. Once sweet potato finally clicked for me, baking with it became so much fun. The combinations feel endless, and this cake pairs it with the oatmeal texture I always want in a fall dessert.
Ingredient notes
Key ingredients
Sweet potato purée
Sweet potato purée gives the cake its warm color, soft texture, and unmistakable sweet potato flavor.
Old-fashioned oats
Old-fashioned oats keep their shape in the filling, creating the chewy oatmeal texture that makes this cake different.
Saigon cinnamon
Saigon cinnamon has a bold, warm flavor, so the measured teaspoon is enough to season the cake without overwhelming the sweet potato.
Vanilla bean glaze
Part of the glaze soaks into the warm cake layers, and the rest finishes the assembled cake with a glossy vanilla bean drip.
Brands I used for this recipe
These are preferences, not requirements. If you choose the non-dairy route, these are the products I test with. Dairy equivalents can be used at the same listed amounts and temperatures.
Forager Unsweetened Plain Yogurt
Plain unsweetened yogurt adds moisture, acidity, and body so the crumb bakes up tender without tasting tangy.
Silk Original Unsweet
Milk affects how smoothly a batter, filling, or frosting comes together. Soy milk and Ripple tend to emulsify well because their protein and fat help create a creamy, cohesive finish.
Country Crock Plant Butter Sticks
Use butter sticks for buttercream and fillings that need to hold their shape.
King Arthur Unbleached Cake Flour
I use King Arthur Unbleached Cake Flour for this recipe.
Rising Star Baking Supply Vanilla Bean Paste
I use Rising Star Baking Supply Vanilla Bean Paste for this recipe.
Testing notes
Why this works
Why the cake layers are poked while warm
The small holes give the reserved vanilla bean glaze somewhere to settle, helping it soak into each layer instead of sitting only on the surface.
How the oatmeal filling keeps its cookie-dough texture
The sugars are melted until glossy while preserving a little texture, helping the filling feel like oatmeal cookie dough.
Why everything cools before assembly
Warm cake or filling can soften the buttercream dam and make the layers slide. Cool every component completely before stacking.
How to judge the glaze
Lift the whisk and watch the glaze fall back into the bowl. The ribbon should remain visible for about 3 seconds before disappearing.
Inside the recipe
How It All Comes Together
From Instagram
Watch the reel
Watch the sweet potato cake, vanilla bean soak, oatmeal caramel, and brown sugar buttercream come together layer by layer.
Open the reel
Troubleshooting
If This Happens
The sweet potato batter is not smooth
Make sure the sweet potato purée is smooth before mixing. Whisk the wet ingredients until they are fully emulsified, then stop mixing the batter as soon as the dry ingredients disappear.
The oatmeal filling became too smooth
Melt the butter and sugars gently and stop once the mixture is glossy. The finished filling should keep some oat texture instead of turning into a completely smooth sauce.
The glaze is sitting on top of the cake
Poke small holes across each layer while it is still warm, then drizzle about 3 tablespoons of glaze over each one. Give the glaze time to soak in before wrapping and chilling the layers.
The cake layers are sliding during assembly
Make sure the cake and oatmeal filling are completely cool. Pipe a tall, closed buttercream dam, keep the filling inside it, and chill the crumb-coated cake until firm.
Before you slice
Texture and serving notes
Bring refrigerated slices to room temperature for 25-30 minutes before serving for the softest cake and filling.
Keep it good
Storage
Fridge
Store the cake covered in the refrigerator for up to 5 days.
Note 2
Keep cut surfaces covered so the cake layers stay soft.
Recipe FAQ
Questions that come up
Can I use vanilla extract instead of vanilla bean paste?
Yes. I prefer vanilla bean paste for its fuller flavor and vanilla bean flecks, but vanilla extract works perfectly well if that is what you have on hand. Use the same amount.
What texture should the oatmeal filling have?
It should stay softly textured like oatmeal cookie dough rather than becoming a completely smooth sauce.
How cool should the filling be before assembly?
Cool it fully to room temperature. If it is still warm, it can soften the buttercream dam and make the stacked cake unstable.
Can I use dairy ingredients?
Yes. I test my recipes with non-dairy ingredients, but you can use the milk, plain unsweetened yogurt, butter, and cream you have on hand while keeping the listed amounts and temperatures the same.
Should I weigh the ingredients or use volume measurements?
I strongly recommend weighing the ingredients in grams for the most reliable result. Volume measurements are included for convenience, but the amount in a cup can change depending on how an ingredient is filled, packed, or poured. These recipes are easy to follow, but their ratios are precise, so I cannot guarantee the exact same result when volume measurements are used. I still use teaspoons and tablespoons for small amounts like leaveners, salt, spices, and flavorings because those are the most practical measurements.
Can I make this recipe gluten-free?
I have not tested this recipe with gluten-free flour, so I cannot guarantee the same texture, rise, or structure. If you would like to experiment, a cup-for-cup (1:1) gluten-free baking blend intended to replace all-purpose flour is the best place to start. Results may differ from the recipe as written.
Can I use all-purpose flour instead of cake flour?
Yes, of course. Replace the cake flour with the same amount of all-purpose flour by weight. The cake will have a slightly sturdier, less delicate crumb, but it will still be great.
More lava cakes to try
- Prep
- 45 min active
- Bake
- 24-26 min
- Total
- About 3 hr, including cooling and assembly
- Yield
- One three-layer 8-inch cake
Measurement note
For the closest match to the recipe I tested, use grams. Volume measurements are included for convenience, but cups can vary, so I cannot guarantee the exact same result when measuring by volume.
Ingredients
Tap each ingredient as you use it.
Sweet Potato Cake Layers
- 330 g cake flour, sifted with the spices
- 15 g cornstarch
- 2 1/2 teaspoons baking powder
- 1/2 teaspoon baking soda
- 1 teaspoon fine sea salt
- 1/8 teaspoon ground nutmeg
- 240 g light brown sugar (packed)
- 100 g granulated sugar
- 1 teaspoon Saigon cinnamon
- 240 g sweet potato purée
- 240 g neutral oil
- 120 g plain unsweetened yogurt
- 260 g milk, room temperature
- 2 1/2 teaspoons apple cider vinegar
- 2 teaspoons vanilla bean paste
Oatmeal Caramel Filling
- 110 g butter
- 200 g light brown sugar (packed)
- 25 g granulated sugar
- 90 g cream
- 90 g old-fashioned oats
- 10 g all-purpose flour
- 1/2 teaspoon ground cinnamon
- 1/4 teaspoon ground nutmeg
- 1 teaspoon vanilla bean paste
- 1/2 teaspoon fine sea salt
Brown Sugar Buttercream
- 340 g butter, room temperature
- 65 g light brown sugar
- 480 g powdered sugar, sifted
- 60 g cream, room temperature
- 1/2 teaspoon fine sea salt
- 1 teaspoon vanilla bean powder
Vanilla Bean Glaze
- 240 g powdered sugar, sifted
- 75-90 g cream
- 1 tablespoon vanilla bean paste
- Pinch of fine sea salt
Pan used
I use Fat Daddio's 8-inch anodized aluminum round cake pans for this recipe.
Instructions
- 1Make the sweet potato cake layers. Preheat the oven to 350°F. Grease three 8-inch round pans and line the bottoms with parchment.
- 2In a medium bowl, whisk together the cake flour, cornstarch, baking powder, baking soda, salt, cinnamon, and nutmeg.
- 3In a large bowl, whisk together the sweet potato purée, light brown sugar, granulated sugar, oil, yogurt, milk, apple cider vinegar, and vanilla bean paste until smooth and emulsified.
- 4Add the dry ingredients to the wet ingredients and whisk just until combined and glossy.
- 5Divide the batter evenly among the prepared pans and tap the pans gently to release air bubbles.
- 6Bake for 24-26 minutes, until the centers spring back and the edges pull slightly from the sides.
- 7Cool the cakes in their pans for 10 minutes, then transfer them to wire racks.
- 8While the layers are still warm, poke small holes evenly over each one with the handle of a thin spatula or a wooden skewer.
- 9Make the vanilla bean glaze. Whisk together the powdered sugar, 75 g cream, vanilla bean paste, and salt until smooth and glossy. Add the remaining cream as needed to reach a 3-second ribbon consistency.
- 10Reserve about 9 tablespoons of glaze for soaking the cake layers. Drizzle about 3 tablespoons over each warm layer and allow it to soak in.
- 11Wrap and chill the cake layers completely in the refrigerator or freezer before filling and frosting.
- 12Make the oatmeal caramel filling. Melt the butter, light brown sugar, and granulated sugar in a saucepan over medium heat until glossy while preserving a little texture.
- 13Whisk in the cream, vanilla bean paste, salt, cinnamon, and nutmeg. Let the mixture bubble for about 30 seconds.
- 14Stir in the oats and all-purpose flour until evenly combined and smooth.
- 15Transfer the oatmeal filling to a bowl and cool fully to room temperature before layering.
- 16Make the brown sugar buttercream. Beat the butter for 2-3 minutes, until light and smooth.
- 17Add the light brown sugar and beat for 2 minutes to begin dissolving the sugar crystals.
- 18Add the powdered sugar in two additions, alternating with the cream.
- 19Add the salt and vanilla bean powder and beat until the buttercream is smooth.
- 20Assemble the cake. Place one chilled cake layer on a cake board and pipe a tall, complete buttercream dam around the edge.
- 21Spread a generous layer of oatmeal caramel inside the dam.
- 22Add the second cake layer and repeat the buttercream dam and oatmeal caramel filling.
- 23Add the final cake layer and press gently to level the cake.
- 24Apply a crumb coat, chill until firm, then frost the sides and top with the remaining brown sugar buttercream.
- 25Pour or spoon the remaining vanilla bean glaze over the top, letting some drip naturally over the edges.
Meet the baker
Angela Heckler
Angela Heckler is the recipe developer, baker, and photographer behind Obsessed Cakes. Her Old-Fashioned Donut Loaf series is a growing collection of cake-donut-inspired loaves with soft, deeply moist crumbs, buttery streusel, and crackly glaze. Angela develops and tests every recipe in her Arizona kitchen. Follow Obsessed Cakes on Instagram, TikTok, and YouTube.
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