For the crust

1. Whisk together the flour, cocoa powder, and salt in a medium bowl. Set aside.
2. Using an electric mixer, beat butter and sugar together until light and creamy. Add egg and vanilla extract; beat until smooth. Add flour mixture and beat at low speed just until dough forms.
3. Divide dough into 6 equal portions. Form portions into slightly flattened disks, wrap in plastic wrap and chill until firm, about one hour.
4. Spray the insides of 6 (4-1/4 inch diameter) tartlet pans with removable bottoms with baking spray. Set aside.
5. On a lightly floured surface, roll out each disk of dough to a 6-inch round. Transfer the rounds to the prepared tartlet pans. Ease dough into the pans and pat firmly into the bottoms and up the sides of the pans, folding edges over to form double-thick sides. Chill dough in tartlet pans until firm, about 30 minutes.
6. Preheat oven to 375 degrees. Remove tartlet pans from the fridge and place on rimmed baking sheet. Dock the bottom of each tart crust with a fork. Bake tartlet shells until set around edges, about 8 minutes. If crusts have puffed up, gently push the crusts down with the back of a small spoon. Cool in pans on cooling rack.

For the filling

1. Preheat oven to 350 degrees F.
2. Whisk sugar and cornstarch together in a small bowl. Set aside.
3. Whisk eggs and egg yolks in a small bowl until blended. Set aside.
4. Melt chocolate and butter together in a medium saucepan over low heat (see notes). Stir in cornstarch mixture until well blended. Mixture will be grainy at this point. Whisk in egg mixture and stir until well blended. Mix in Grand Marnier, if using.
5. Spread 1 teaspoon of jam into bottom of each pre-baked crust. Arrange raspberries in crusts, dividing equally and spacing evenly. Spoon chocolate mixture over berries, equally dividing the batter among the tartlet pans. Bake tartlets for 25 to 28 minutes or until filling puffs around edges and a cake tester inserted in the center comes out with moist crumbs clinging to it (it is better to undercook than overcook.). Cool 10 minutes in pans on cooling rack. Carefully remove pan sides from tartlets. Place tartlets on plates. Spoon sweetened whipped cream alongside or on top and serve warm.