Rhubarb Mousse Cake

Rhubarb Mousse Cake

Rhubarb Mousse Cake offers a delightful end to any celebration, with curls of candied rhubarb adding the crowning touch to dense white chocolate cake and perfectly pink mascarpone mousse.

Rhubarb Mousse Cake
Make 1 (9-inch square) cake
  • 2 ounces white chocolate, chopped
  • 2 tablespoons unsalted butter, cubed
  • ¼ cup whole milk
  • ½ cup all-purpose flour
  • ½ teaspoon baking powder
  • ⅛ teaspoon salt
  • 1 egg
  • ¼ cup granulated sugar
  • ½ teaspoon vanilla extract
  • Rhubarb-Mascarpone Mousse (recipe follows)
  • Rhubarb Ribbon (recipe follows)
  1. Preheat oven to 325º. Line a 9-inch square baking pan with parchment paper, letting excess extend over sides.
  2. In a small saucepan, heat chopped white chocolate, cubed butter, and milk over low heat until chocolate and butter have melted. Keep warm.
  3. In a small bowl, whisk together flour, baking powder, and salt.
  4. In the bowl of a stand mixer fitted with the whisk attachment, beat egg, sugar, and vanilla extract at medium speed until tripled in volume and pale in color. (If you lift the whisk and draw an 8 on the top of the batter, you should be able to see the whole 8 before it disappears.) Add flour mixture, and beat at low speed until combined. Add melted white chocolate mixture, and beat until smooth. Pour batter into prepared pan.
  5. Bake until a wooden pick inserted in the center comes out clean, 15 to 20 minutes. Let cool in pan for 10 minutes; using excess parchment as handles, gently remove from pan. Still on parchment, let cool completely on a wire rack. Place a paper towel over top of cake and lightly spray outside edges of parchment with cooking spray before returning cake, still on parchment, to pan.
  6. Pour Rhubarb-Mascarpone Mousse over prepared cake, and smooth top; tap pan gently on counter to remove any large air bubbles. Refrigerate until set, at least 2 hours.
  7. Using excess parchment as handles, transfer from pan to a work surface. Using a serrated knife, slice into 4x1½-inch bars. Top each with a piece of Rhubarb Ribbon, and serve immediately. Store, covered, in refrigerator.

Rhubarb-Mascarpone Mousse
  • 2 pounds rhubarb, cut into 1-inch pieces
  • 1½ cups granulated sugar, divided
  • ½ cup water, divided
  • 3 teaspoons unflavored gelatin (less than 2 envelopes)
  • 8 ounces mascarpone
  • ¾ cup chilled heavy whipping cream
  • 1 teaspoon vanilla extract
  1. In a large saucepan, heat rhubarb, 1¼ cup water over medium-high heat. Cook, stirring occasionally, until rhubarb releases enough juice to almost cover rhubarb, 5 to 8 minutes. Reduce heat and simmer, stirring occasionally, until rhubarb falls apart and is reduced to approximately 4 cups, 25 to 30 minutes. Remove from heat.
  2. Strain mixture through a large fine-mesh sieve set over a bowl. Transfer pulp to another bowl, and use as a jam, if desired.
  3. In a small bowl, whisk together gelatin and remaining ¼ cup water; let stand until softened, about 1 minute. Stir gelatin mixture into hot rhubarb mixture until dissolved.
  4. Set bowl inside a larger bowl of ice water, and stir rhubarb mixture until cooled to room temperature.
  5. In the work bowl of a stand mixer fitted with the whisk attachment, beat mascarpone, cream, vanilla extract, and remaining ¼ cup sugar at medium speed until stiff peaks form. Slowly add rhubarb mixture, beating at low speed until combined and smooth.

Rhubarb Ribbon
  • 1 cup water
  • 1 cup granulated sugar
  • 3 stalks rhubarb, thinly shaved and halved
  1. Preheat oven to 225º. Line a sheet pan with parchment.
  2. In a small saucepan, bring 1 cup water and sugar to a boil over medium-high heat; reduce heat and simmer until sugar is dissolved. Remove from heat. Add rhubarb and let steep for 4 minutes. Remove rhubarb from simple syrup and lie flat on prepared pan.
  3. Bake for 15 minutes. Remove from oven and loosely wrap each piece around a wooden spoon handle. Bake for 10 minutes, and check for dryness. If rhubarb is still tacky, bake 5 minutes more. Gently remove from spoons, and store on paper towels in a sealed container until ready to use.
Note: If rhubarb doesn’t hold its shape after baking, return ribbons to the oven for a few minutes to further dehydrate.

To find more rhubarb recipes, see “Blushing Rhubarb” in the March/April 2020 issue, available at Victoriamag.com.

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