Riesling Rhubarb Crisp Cake
Author: 
Serves: 1, 8-inch round, 3-layer cake
 
This cake, from the book Layered by Tessa Huff, is flavored with sweet riesling, layered with tart rhubarb buttercream and bits of crisp oat crumble, and generously frosted with luscious swiss meringue buttercream.
Ingredients
  • for the riesling cake:
  • butter or nonstick cooking spray for the pans
  • 3¼ cups cake flour
  • 1 tablespoon plus ½ teaspoon baking powder
  • ¾ teaspoon salt
  • 1 cup (2 sticks) unsalted butter, at room temperature
  • 2 cups granulated sugar
  • 2 teaspoons pure vanilla extract
  • 6 large egg whites
  • 1½ cups sweet riesling
  • for the rhubarb strawberry compote:
  • 8 ounces fresh strawberries, hulled and quartered
  • 4 ounces fresh rhubarb cut into ¼ inch pieces
  • ¼ cup granulated sugar
  • 2 tablespoons fresh lemon juice
  • for the oat crumble:
  • ½ cup quick cooking rolled oats
  • ¼ cup sliced almonds
  • ¼ cup firmly packed brown sugar
  • ¼ cup all-purpose flour
  • 3 tablespoons unsalted butter, at room temperature
  • 2 tablespoons honey
  • ½ teaspoon ground cinnamon
  • ¼ teaspoon salt
  • for the rhubarb buttercream:
  • 2 medium recipes Vanilla Swiss Meringue Buttercream (below)
  • ½ cup rhubarb strawberry compote
  • for the vanilla swiss meringue buttercream (one medium recipe*):
  • ½ cup plus 2 tablespoons large egg whites
  • 1¼ cups granulated sugar
  • 2 cups (4 sticks) unsalted butter, at room temperature
  • 2 teaspoons pure vanilla extract
  • pink gel food coloring
Instructions
  1. Make the riesling cake:
  2. Preheat the oven to 350°F. Grease 3, 8-inch round, cake pans and line with parchment circles.
  3. Sift together the flour, baking powder, and salt. Set aside.
  4. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until smooth. Add the sugar and mix on medium-high until the butter is light and fluffy, 3-5 minutes. Stop the mixer and scrape down the bowl.
  5. Turn the mixer to medium and gradually add the vanilla and egg whites until combined. Stop the mixer and scrape down the bowl.
  6. Turn the mixer to low and add the flour mixture in three batches, alternating with the riesling, beginning and ending with the flour mixture. Mix on medium speed for no longer than 30 seconds after the last streaks of the dry ingredients are combined.
  7. Evenly divide the batter among the prepared pans. Bake for 23-25 minutes, or until a toothpick inserted in the center of the cakes comes out clean. Let them cool on a wire rack for 10-15 minutes before removing the cakes from their pans.
  8. Make the rhubarb strawberry compote:
  9. Combine the strawberries, rhubarb, sugar, and lemon juice in a medium saucepan and cook them over medium-high heat, stirring intermittently with a wooden spoon, until the juices start to bubble. Reduce the heat to maintain a simmer and cook for 8 to 10 minutes, or until the fruit starts to break down. Remove the pan from the heat and let cool.
  10. Make the oat crumble:
  11. Preheat the oven to 375°F. Line a baking sheet with parchment paper.
  12. In a medium bowl, mix together the oats, almonds, brown sugar, flour, butter, honey, cinnamon, and salt with a wooden spoon until combined. The mixture should resemble clumps of sand. Sprinkle it over the lined baking sheet and bake, stirring halfway through, for 8 to 10 minutes, or until golden brown. Let it cool and crumble the mixture into smaller pieces.
  13. Make the rhubarb buttercream:
  14. In the bowl of a stand mixer fitted with the paddle attachment, mix 2 cups of the buttercream (instructions below) until silky and smooth. Add ½ cup of the cooled rhubarb compote and mix until combined.
  15. Make the vanilla swiss meringue buttercream:
  16. Place the egg whites and sugar in the bowl of a stand mixer. Whisk them together by hand to combine. Fill a medium saucepan with a few inches of water and place it over medium-high heat. Place the mixer bowl on top of the saucepan to create a double boiler. The bottom of the bowl should not touch the water.
  17. Whisking intermittently, heat the egg mixture until it registers 160°F on a candy thermometer or is hot to the touch. Once hot, carefully fit the mixer bowl to the stand mixer.
  18. With the whisk attachment, beat the egg white mixture on high speed for 8 to 10 minutes, until it holds medium-stiff peaks. When done the outside of the bowl should return to room temperature and no residual heat should be escaping the meringue out of the top of the bowl. Stop the mixer and swap out the whisk attachment for the paddle.
  19. With the mixer on low speed, add the butter, a few tablespoons at a time, then the vanilla. Once incorporated, turn up the mixer speed to medium-high and beat until the buttercream is silky and smooth, 3 to 5 minutes.
  20. To assemble the cake:
  21. Once the cakes have completely cooled, level them and choose which layer will be the bottom. Place it on a cake plate or serving dish. Spread on half of the rhubarb buttercream with an offset spatula. Sprinkle with ½ to ¾ cup of the oat crumble. Top with the next layer of the cake and repeat with the buttercream and remaining crumble, finishing with the final layer.
  22. Add gel food coloring, if using, to the remaining buttercream. Use it to frost the top and sides of the cake (however you would like). Top with fresh strawberries (if you want) and serve with the remaining compote.
Notes
To frost this cake as shown, use *two recipes of the buttercream (just double the ingredients for the vanilla swiss meringue buttercream).

I left some larger clumps of crumble in the cake which made it really difficult to cut cleanly, next time I would make sure the crumble is in much smaller pieces.
Recipe by hungrygirlporvida.com at http://www.hungrygirlporvida.com/blog/2016/04/18/riesling-rhubarb-crisp-cake/