Preheat your oven to 350°F. In a bowl, stir together the gluten free chocolate cookie crumbs and melted butter until evenly moistened. Press the mixture firmly into the bottom and up the sides of a 9-inch pie dish. Bake for 8 minutes, then remove and set aside.
For the brownie layer, melt the butter and chopped unsweetened chocolate together in a saucepan over low heat, stirring constantly until smooth. Remove from heat and let cool for 5 minutes.
Whisk the granulated sugar, eggs, and vanilla extract into the chocolate mixture until smooth. Fold in the gluten free 1-to-1 baking flour and salt until just combined.
Pour the brownie batter into the pre-baked crust and bake for 25-28 minutes, until the brownie layer is set but still slightly fudgy in the center.
Remove the pie from the oven and immediately scatter the mini marshmallows evenly over the hot brownie layer. Return to the oven for 3-4 minutes, just until the marshmallows puff up and turn lightly golden. Let the pie cool completely, then refrigerate for at least 2 hours.
Using an electric mixer, whip the heavy cream, powdered sugar, and cocoa powder together until stiff peaks form. Spread or pipe the chocolate whipped cream over the marshmallow layer.
Garnish with chocolate shavings and refrigerate for at least 30 minutes before slicing. Serve chilled.