For the Dough:
1. Combine butter and sugar in a large mixing bowl; beat on medium speed until light and fluffy. Add the egg and vanilla and continue mixing until incorporated. Add the flour and continue mixing until just combined. Remove dough from mixer bowl and tightly wrap in plastic wrap. Refrigerate at least 1 hour.
2. Roll out dough on a lightly floured surface to ⅛-inch thickness. Cut circular disks about 1-inch larger than tartlet pan being used. Press the dough into the pan and trim the top edge. Freeze until firm, about 30 minutes.
3. Preheat oven to 325°F. Prick each shell with a fork several times and bake for 20 minutes or until lightly golden brown.
For the Ganache Filling:
1. Preheat oven to 325°F.
2. Heat heavy cream and 2 tablespoons of sugar in a saucepan over low heat until it reaches a gentle boil.
3. In a separate bowl, whisk together the egg yolks and remaining sugar. Slowly add the hot cream mixture to the egg yolks in 3 increments, whisking constantly.
4. Break the chocolate bar into pieces and add to the hot yolk/cream mixture. Let stand for 2-3 minutes so the chocolate can melt. Once melted, continue whisking until fully combined. Pour the ganache filling through a mesh strainer, then transfer to the prepared tartlet shells, leaving ⅛- inch at the top.
5. Bake 15 minutes or until the ganache sets. Let cool to room temperature before serving. Garnish with whipped cream and raspberries if desired.
Makes 6, 4-inch tartlets.