Rhubarb Mascarpone Mousse Cake
It's rhubarb season here, and this time of year I find myself wondering what tasty things I can do with it besides making a crisp/crumble (I've already made three of those). When searching for a birthday dessert to make for a coworker who loves rhubarb, I ran across this recipe on Epicurious. At first I passed it by, thinking 'too complicated'. But...it looks so pretty and pink and...downright girly, I thought. I just had to give the instructions another look. Turns out it wasn't too bad. In spite of my lack of a lot of experience messing with gelatins and mousses, and this taking me days to make in stages between working/sleeping, it came together nicely. The cake is so moist buried in the mousse, and with its strawberry filling. The mousse alone is wonderfully creamy with just the right amount of rhubarb flavor.
Cake:
1 cup all purpose flour
1 teaspoon baking powder
1/4 teaspoon salt
1/2 stick (4 tablespoons) unsalted butter, softened
1/2 cup sugar
1 large egg, at room temperature 30 minutes
1 teaspoon vanilla
1/3 cup whole milk
1/2 cup strawberry or strawberry-rhubarb jam
Rhubarb-mascarpone mousse:
2 pounds rhubarb, cut into 1-inch pieces (8 cups)
1 1/2 cups sugar, divided
1/2 cup water, divided
3 teaspoons unflavored gelatin (less than 2 packages)
1 cup (8 ounces) mascarpone
3/4 cup chilled heavy cream
1 teaspoon vanilla
Vegetable oil for greasing pan
Glaze:
1 1/2 teaspoons unflavored gelatin
3 tablespoons water
1 cup rhubarb syrup (see below)
Accompaniment:
A few small strawberries, such as tri-star or wild strawberries with their leaves (optional)
Special equipment: 1 (9-inch) round cake pan; 1 (10-inch) round spring-form pan with removable bottom
Preparation
Make cake:
Preheat oven to 350°F and place rack in center.
Butter 9-inch cake pan and line bottom with a round of parchment.
Butter paper, then dust pan with flour, knocking out excess.
Sift together flour, baking powder, and salt into a bowl.
Beat butter and sugar together at medium-high speed until pale and fluffy, about 2 minutes.
Beat in egg and vanilla until fluffy and combined well, about 2 minutes.
Reduce speed to low and add flour mixture and milk alternately in 3 batches, beginning and ending with flour. Mix until batter is just combined. Do not overmix.
Spread batter evenly in pan and bake until cake begins to pull away from sides of pan and a wooden pick or skewer inserted in center comes out clean, 20 to 25 minutes (cake will still be pale in color, not golden brown).
Cool for 10 minutes in pan on a rack, then invert onto rack and reinvert to cool completely right side up.
Make mousse while cake is baking:
Combine rhubarb, 1 1/4 cups sugar, and 1/4 cup water in a large heavy saucepan and cook over medium-high heat, stirring occasionally, until rhubarb releases enough juice to almost cover rhubarb, 5 to 8 minutes.
Reduce heat and simmer mixture, stirring occasionally, until rhubarb falls apart and is reduced to about 4 cups, 25 to 30 minutes. Remove from heat.
Pour mixture into a large fine-mesh sieve set over a bowl and collect 1 cup syrup and set aside. Transfer rhubarb pulp to another bowl.
Soften gelatin in remaining 1/4 cup water 1 minute, then stir into hot rhubarb mixture until dissolved.
Set bowl inside a larger bowl of ice water and stir rhubarb mixture until cooled to room temperature (do not let set on ice).
Beat together mascarpone, heavy cream, and vanilla with remaining 1/4 cup sugar until it just holds stiff peaks.
Fold cooled rhubarb mixture into mascarpone mixture.
Assemble mousse cake:
Carefully halve cooled cake horizontally, then spread jam on bottom half and reassemble.
Invert bottom of spring-form pan (to make it easier to slide cake off bottom), then lock on side. Lightly oil bottom and sides of pan with some vegetable oil.
Arrange cake in center of spring-form pan. Spoon rhubarb mousse into pan over cake. Smooth top. Rap pan on counter twice to release any air bubbles and chill cake, uncovered, until mousse is set, at least 2 hours.
Make glaze:
Sprinkle gelatin over water in a small heavy saucepan to soften, 1 minute. Heat gelatin over low heat until it has dissolved. Remove from heat then stir in reserved rhubarb syrup.
Pour glaze over chilled mousse, tilting pan slightly to cover it completely in an even layer. Chill, uncovered, until glaze is set, at least 1 hour.
To serve:
Let cake stand at room temperature 30 minutes to soften slightly. Wrap a kitchen towel dampened in hot water around the side of the pan for about 15 seconds. Run the tip of a thin knife around the edge of the pan, then gently unlock and remove sides of spring-form pan.
Cooks' Notes:
•Mousse cake can be made 1 day ahead and kept chilled. Loosely cover with plastic wrap once glaze is set (use toothpicks to keep plastic wrap from touching glaze, if necessary).
The cake is not that deep, so careful splitting with a good knife is necessary
I kept thinking of salmon spread while I was working with the mousse
I couldn't find my off-set spatula, so I leveled off the mousse with the back of a big spoon
Not level enough, apparently. This to me is the biggest drawback of this recipe. Nothing you can do at this point (other than conjuring more syrup) will result in the pristine pink top layer pictured on the Epicurious website. And the syrup started to leak out the seam in my springform pan. I quickly got it in the fridge, hoping it would gel and stop the hemorrhage (it did). What else to do?
Disguise it with a big ol' garnish! Violet, mint and lemon balm leaves, plus some strawberry and blackberry blossoms, and violets. No early strawberries (or any later, for that matter) in my yard, as suggested in the recipe. The chipmunks eat them all while they are still green.
Notes:
---Draining the syrup from the pulp took FAR longer than indicated. Even with a small colander, it took most of a day in the fridge, and I had to stir a little more water into the pulp to barely reach a cup.
---I stirred a little rhubarb into the strawberry jam, and a little strawberry jam into the rhubarb pulp, just to more evenly distribute the flavors and boost the color of the mousse and syrup/gel.
---I think I would reduce the sugar a little. The jam and cake provide plenty of sweetness.
---I'd make this again, but maybe re-tool it as a trifle or individual parfaits. The mousse still stuck to the sides of the springform pan, and it's a bit hard to keep the whole thing neat and tidy.
