In a mixing bowl, combine flour, powdered sugar, cocoa powder, salt, and granulated sugar.
Cut in cold cubed butter until mixture becomes crumbly.
Add the cold egg and mix until a dough forms. Chill the dough for 30 minutes.
Roll out the dough and press into tart molds. Prick the surface with a fork.
Bake tart shells at 350°F (175°C) for 15-20 minutes. Let cool completely.
For raspberry jam, heat raspberries and granulated sugar in a saucepan.
Stir in pectin and simmer for 5-7 minutes until thickened. Cool completely.
For mousse, warm milk, black sesame paste, and heavy cream until just warm.
Add white chocolate, stirring until melted. Mix in bloomed gelatin and salt.
Cool slightly, then gently fold in whipped cream. Chill until mousse is pipeable.
To make brandy snaps, melt butter, brown sugar, and corn syrup together.
Remove from heat and stir in flour, salt, brandy (optional), and toasted black sesame seeds.
Spoon small rounds onto a lined baking sheet and bake at 350°F (175°C) for 6-8 minutes until golden.
Cool brandy snaps until crisp.
To assemble, spread raspberry jam in tart shells, pipe or spoon mousse on top.
Arrange fresh raspberries over the mousse and garnish with brandy snaps.