Combine flour, powdered sugar, cocoa powder, salt, and granulated sugar in a bowl.
Cut in the cold butter until mixture resembles coarse crumbs.
Add cold egg and mix until dough forms. Wrap and chill for 30 minutes.
Roll out dough and line tart molds. Chill for 15 minutes.
Bake at 350°F (175°C) for 15–18 minutes until set. Cool completely.
To make raspberry jam, heat raspberries and sugar in a saucepan.
Mix pectin with a little sugar and add to the raspberries. Cook 2–3 minutes until thickened.
Blend if desired and let cool.
Heat milk and heavy cream until warm. Stir in white chocolate until melted.
Add black sesame paste and salt, then stir in bloomed gelatin until dissolved.
Cool mixture slightly, then fold in whipped cream until smooth and airy.
For brandy snaps, melt butter, brown sugar, and corn syrup in a saucepan.
Remove from heat, stir in brandy (optional), flour, salt, and sesame seeds.
Spoon small circles of batter onto parchment and bake at 355°F (180°C) for 6–8 minutes until golden.
Cool until crisp.
Spread raspberry jam in tart shells, pipe or spoon mousse on top, arrange fresh raspberries, and garnish with brandy snaps.