Make the Chocolate Shortbread Crust by combining chocolate, butter, and salt until it resembles coarse crumbs. Shape into a disk, wrap in plastic wrap, and chill for 30 minutes.

Preheat the oven to 350°F (175°C). Roll out the crust and fit it into the pie plate. Blind bake for 15-20 minutes until set, then cool completely.

Prepare the chocolate filling by melting butter and milk chocolate together. Stir in sugar, cocoa powder, flour, salt, and eggs until creamy. Strain for a smooth texture.

Pour filling into the cooled crust and bake for 25-30 minutes until edges are set. Let cool completely.

Make the marshmallow topping by whisking egg whites and sugar over a double boiler until fluffy. Optionally add cream of tartar.

Spread the marshmallow topping evenly over the filling and toast lightly with a kitchen torch.

Let the pie rest for 30 minutes before serving to meld flavors and achieve perfect warmth.