Obsessed Cakes

Sweet Potato & Oatmeal Caramel Lava Cake

Warmly spiced sweet potato cake layered with chewy oatmeal caramel, brown sugar buttercream, and a glossy vanilla bean glaze.

Prep
45 min active
Bake
24-26 min
Total
About 3 hr, including cooling and assembly
Yield
One three-layer 8-inch cake

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Ingredients

Sweet Potato Cake Layers

  • 330 g (2 3/4 cups) cake flour , sifted with the spices
  • 15 g (2 tablespoons + 1/2 teaspoon) cornstarch
  • 2 1/2 teaspoons baking powder
  • 1/2 teaspoon baking soda
  • 1 teaspoon fine sea salt
  • 1/8 teaspoon ground nutmeg
  • 240 g (1 1/8 cups, packed) light brown sugar
  • 100 g (1/2 cup) granulated sugar
  • 1 teaspoon Saigon cinnamon
  • 240 g (1 cup) sweet potato purée
  • 240 g (1 1/8 cups) neutral oil
  • 120 g (1/2 cup) plain unsweetened yogurt
  • 260 g (1 1/8 cups) milk , room temperature
  • 2 1/2 teaspoons apple cider vinegar
  • 2 teaspoons vanilla bean paste

Oatmeal Caramel Filling

  • 110 g (1/2 cup) butter
  • 200 g (1 cup, packed) light brown sugar
  • 25 g (2 tablespoons) granulated sugar
  • 90 g (3/8 cup) cream
  • 90 g (1 cup) old-fashioned oats
  • 10 g (1 tablespoon + 1 teaspoon) 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 (1 1/2 cups) butter , room temperature
  • 65 g (1/3 cup) light brown sugar
  • 480 g (3 7/8 cups) powdered sugar , sifted
  • 60 g (1/4 cup) cream , room temperature
  • 1/2 teaspoon fine sea salt
  • 1 teaspoon vanilla bean powder

Vanilla Bean Glaze

  • 240 g (1 7/8 cups) powdered sugar , sifted
  • 75-90 g (1/3 cup to 3/8 cup) cream
  • 1 tablespoon vanilla bean paste
  • Pinch of fine sea salt

Instructions

  1. Make the sweet potato cake layers. Preheat the oven to 350°F. Grease three 8-inch round pans and line the bottoms with parchment.
  2. In a medium bowl, whisk together the cake flour, cornstarch, baking powder, baking soda, salt, cinnamon, and nutmeg.
  3. In 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.
  4. Add the dry ingredients to the wet ingredients and whisk just until combined and glossy.
  5. Divide the batter evenly among the prepared pans and tap the pans gently to release air bubbles.
  6. Bake for 24-26 minutes, until the centers spring back and the edges pull slightly from the sides.
  7. Cool the cakes in their pans for 10 minutes, then transfer them to wire racks.
  8. While the layers are still warm, poke small holes evenly over each one with the handle of a thin spatula or a wooden skewer.
  9. Make 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.
  10. Reserve about 9 tablespoons of glaze for soaking the cake layers. Drizzle about 3 tablespoons over each warm layer and allow it to soak in.
  11. Wrap and chill the cake layers completely in the refrigerator or freezer before filling and frosting.
  12. Make 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.
  13. Whisk in the cream, vanilla bean paste, salt, cinnamon, and nutmeg. Let the mixture bubble for about 30 seconds.
  14. Stir in the oats and all-purpose flour until evenly combined and smooth.
  15. Transfer the oatmeal filling to a bowl and cool fully to room temperature before layering.
  16. Make the brown sugar buttercream. Beat the butter for 2-3 minutes, until light and smooth.
  17. Add the light brown sugar and beat for 2 minutes to begin dissolving the sugar crystals.
  18. Add the powdered sugar in two additions, alternating with the cream.
  19. Add the salt and vanilla bean powder and beat until the buttercream is smooth.
  20. Assemble the cake. Place one chilled cake layer on a cake board and pipe a tall, complete buttercream dam around the edge.
  21. Spread a generous layer of oatmeal caramel inside the dam.
  22. Add the second cake layer and repeat the buttercream dam and oatmeal caramel filling.
  23. Add the final cake layer and press gently to level the cake.
  24. Apply a crumb coat, chill until firm, then frost the sides and top with the remaining brown sugar buttercream.
  25. Pour or spoon the remaining vanilla bean glaze over the top, letting some drip naturally over the edges.