2 sticks (16 tablespoons) unsalted butter
8 ounces fine-quality bittersweet chocolate
12 ounces blanched almonds
6 extra-large eggs, separated
1 tablespoon espresso powder
¼ teaspoon almond extract
1 cup sugar
6 tablespoons confectioners’ sugar
12-14 ounces mascarpone*
1 very large lemon
*Note: We doubled the mascarpone recipe for 10 people
Preheat oven to 325 degrees. Place rack in bottom third of the oven. Using 1 tablespoon butter, butter bottom and sides of a 10-inch removable bottom cake pan. Line the bottom with a round of parchment paper and butter the paper.
Melt the remaining butter and chocolate in a heavy saucepan over low heat until melted and smooth, stirring often.
Process the almonds in two batches, each with 2 tablespoons sugar, until very fine and powdery. Transfer to a large bowl. Stir in espresso powder. Set aside.
Beat yolks until light and thick, about 3 minutes. Add ½ cup sugar and beat 2 minutes longer. Add the melted chocolate and the almond extract to the yolks. Stir well. Stir in the ground almonds until thoroughly mixed. Beat egg whites with a pinch of salt and ¼ cup remaining sugar until very stiff. Add beaten whites to the batter in 2 batches until incorporated. Pour batter into prepared pan.
Bake on a rack placed in the bottom third of the oven for 1 to 1-1/4 hours or until the cake is just firm. Cool and invert. Remove paper. Dust with 2 tablespoons confectioners sugar pushed through a sieve.
Lemon mascarpone: Beat mascarpone with 6 tablespoons confectioners sugar. Grate the lemon zest and add to mascarpone with 1 to 2 teaspoons lemon juice and a large pinch of salt. Refrigerate until about 1 hour before serving. Whip gently with a large fork and serve a large dollop with each slice of cake.
Note: If the lemon mascarpone is too thick, you can add a teaspoon or so of milk or light cream and whip again.