1. In a small bowl sift together flour, baking soda, and salt, then whisk to mix evenly. In a food processor, pulse the sugars until very fine. With the motor running, add the butter, then the peanut butter and process until smooth and creamy. Add the egg and vanilla until incorporated. Add the flour mixture until mixed together. Scrape the dough into a bowl. Cover and refrigerate at least 1 hour or overnight.
2. Heat oven to 375 degree F. Press the dough evenly into a 9-inch tart pan. Bake until golden brown, 10 to 12 minutes. Cool.Make peanut-butter mousse::
3. In a mixer bowl on medium speed beat cream cheese, peanut butter, and sugar until uniform in color. On low speed, add vanilla. Beat in 1/4 cup of the whipped cream just until combined. With a rubber spatula, fold in remaining cream. Scrape the mousse into tart shell and smooth the surface so that it is level. Refrigerate.Make ganache::
4. Meanwhile, break up chocolates into the bowl of a food processor. Pulse until finely ground. In a small saucepan, bring cream to a boil. With the motor running, immediately pour hot cream through the feed tube onto the chocolate. Process until smooth. Add vanilla and pulse a few times to incorporate. Pour the ganache into a bowl and let cool to room temperature. Pour the ganache over peanut-butter mousse in a circular motion. Spread to the edges. Refrigerate at least 2 hours to set before serving. Makes 6 to 8 servings.