Crush the chocolate sandwich cookies in a food processor until they are fine crumbs with no large chunks. Alternatively, place the cookies in a zip-top bag and crush them with a rolling pin. In a bowl, combine the cookie crumbs with the melted butter, granulated sugar (if using), and a pinch of salt. Stir until the mixture looks like damp sand and holds together when pinched.

Pour the crumb mixture into a 9-inch pie dish. Press it firmly across the bottom and up the sides using the bottom of a measuring cup or your fingers. Pack it in well so the crust holds together when sliced. Place the crust in the freezer for at least 15–20 minutes while you prepare the filling.

In a medium saucepan over low heat, combine the mini marshmallows and milk. Cook, stirring constantly, until the marshmallows are completely melted and the mixture is smooth. Do not walk away, as marshmallows can scorch easily. Remove from the heat and let the mixture cool to room temperature, about 15–20 minutes; it should not be warm when you add the whipped cream.

In a large mixing bowl, whip the cold heavy whipping cream with an electric mixer on medium-high speed until soft peaks form. The peaks should be pillowy and gently hold their shape. Avoid over-whipping, which can make the filling grainy.

Once the marshmallow mixture has cooled to room temperature, stir in the green creme de menthe, white creme de cacao, peppermint extract, vanilla extract, a pinch of salt, and a few drops of green food coloring if using. Taste carefully and adjust the peppermint or color as needed; it should taste like a sweet, minty cocoa with a light boozy note.

Gently fold the whipped cream into the mint marshmallow mixture in two or three additions. Use a spatula and a light, folding motion, turning the bowl as you go, to keep as much air in the whipped cream as possible. The mixture should be light, fluffy, and evenly combined.

Remove the chilled crust from the freezer and pour the creamy mint filling into it. Smooth the top with a spatula. If desired, gently tap the pie dish on the counter to release any large air bubbles.

Cover the pie tightly with plastic wrap or foil and place it in the freezer. Freeze for at least 4 hours, or preferably overnight, until the pie is firm enough to slice cleanly but still creamy when served.

Right before serving, top the pie with whipped cream or whipped topping and garnish with chocolate shavings, mini chocolate chips, or crushed chocolate cookies. If the pie is very firm, let it sit at room temperature for 10–15 minutes to soften slightly. Use a sharp knife dipped in warm water and wiped dry between cuts for neat slices.