Blackberry Mouse
1 teaspoon unflavored gelatin
3 tablespoons cold water
1 cup blackberries
1/4 cup granulated sugar
1 egg white
3/4 cup heavy cream
Blackberry syrup
3/4 cup water
1/3 cup granulated sugar
Finely grated zest of 1 lemon, plus more for garnish
1 cup blackberries, plus more for garnish
Other
Lemon cookies, crumbled
Mascarpone cheese
Mint leaves
In a small bowl, sprinkle the gelatin over 1 tablespoon of the water and let stand until softened, about 5 minutes. In a blender, puree the blackberries with the remaining two tablespoons of water. Strain the blackberry purée into a small saucepan; there should be about 3/4 cup. Add the sugar and bring to a boil. Simmer the blackberry mixture over moderate heat, stirring occasionally, until it is slightly reduced, about 5 minutes. Stir in the softened gelatin until dissolved. Let the mixture cool.
In a medium bowl, using an electric mixer, beat the egg white until firm peaks form. Using a rubber spatula, fold in the cooled berry purée until no streaks of white remain. In another bowl, beat the heavy cream until softly whipped. Fold the whipped cream into the berry mixture and refrigerate until chilled, about 1 hour.
In a small saucepan, combine the water and sugar and bring to a boil. Remove from the heat. Add the lemon zest and let stand for 30 minutes. Strain the syrup into a cup. Wipe out the saucepan and return the syrup to it. Add the blackberries to the syrup and bring to a boil. Reduce the heat to low and cook, crushing the blackberries against the side of the pan, until the liquid is slightly reduced and the berries have broken down, about 15 minutes. Strain the syrup into a heatproof cup without pressing. Refrigerate the syrup until chilled.
In a deep coupe or brandy glass, scoop mousse into the glass, then a small scoop of mascarpone cheese. Drizzle the blackberry syrup and top with crumbled lemon, fresh whole blackberries and lemon zest. Top with fresh mint leaves.