Preheat the oven to 350 degrees and butter a 9-inch tart shell with a removable bottom.

Make the chocolate shortbread dough: In a food processor, pulse the almonds until they are finely ground. Add the flour, sugar, unsweetened cocoa powder, and vanilla; pulse until combined. Add the softened butter, pulsing until coarse crumbs form with no large butter lumps (dough should clump together when pinched with fingers).

Immediately transfer the dough to the prepared tart pan. Using your fingers or the bottom of a measuring cup, evenly press dough into the bottom of the shell and up the sides of the pan.

Bake the shell in the center of the oven until golden brown and firm to the touch, about 20 to 25 minutes. Transfer the shell to a wire rack to cool completely before filling with ganache.

Make the ganache filling: Place the chopped chocolate into a medium-size bowl along with kosher salt and vanilla. Set aside. In a small saucepan over medium heat, bring the heavy whipping cream to a bare simmer. Pour immediately over the shaved chocolate, salt, and vanilla. Cover and let sit for 4 to 5 minutes. Once the chocolate has begun to melt, with a wire whisk, stir from the inside out until the chocolate is completely combined, smooth and silky. Pour into the cooled, baked tart shell. Cover loosely and refrigerate for 6 hours and up to 3 days.

Once set, slice and serve topped with sliced almonds, sea salt, or anything else that sounds good!