Preheat the oven to 350°. Put the cookies in a food processor and pulse until you have fine crumbs Place the cookie crumbs into a medium bowl, pour the melted butter over top, and stir to combine. Press about 3  tablespoons of the crumb mixture evenly into 8 mini tart pans onto the bottom and up the sides. Bake at 350 for 8 minutes. Remove the pans from the oven and allow them to cool on a wire rack.

Place the chopped chocolate in a small bowl. In a small saucepan, heat the heavy cream until tiny bubbles form around the edge. Do not let it come to a boil. Pour the cream over the chocolate and let it sit for 5 minutes. Then gently stir to combine them together until it is smooth and creamy.  If there are still some large lumps while you are stirring, you can let it set for a few more minutes before stirring again.

Fill the mini tart crusts with the ganache and smooth them with a spatula if needed. Allow 2-4 hours for the ganache to set. Remove the tarts from the pans and garnish with fresh berries and chopped pistachios if desired, just before serving.