Preheat your oven to 325°F (163°C). In a large mixing bowl, sift together all-purpose flour, powdered sugar, almond flour, cocoa powder, and salt until well combined.

Cut in the cold butter using a pastry cutter or your fingertips until the mixture resembles coarse crumbs.

Add in a beaten egg and mix until a soft dough forms. Wrap in plastic wrap and refrigerate for 10-15 minutes.

On a lightly floured surface, roll out the chilled dough to about 1/8 inch thick and cut into circles for tart rings.

Freeze the shaped dough in the tart rings for 30 minutes.

Bake the chilled tart shells for 12-15 minutes until dry and firm. Let cool completely.

Heat heavy cream in a saucepan until steamy, then pour over finely chopped semisweet chocolate and stir until smooth.

Whip the remaining heavy cream with powdered sugar until soft peaks form, then gently fold into the chocolate mixture.

Fill the cooled tart shells with the chocolate mousse and chill for at least 4 hours.

Before serving, drizzle reserved ganache over each tart and garnish as desired.