Preheat oven to 350°F.

In a medium mixing bowl, stir together the finely ground chocolate cookie crumbs and melted unsalted butter until the mixture resembles wet sand.

Press the chocolate cookie mixture evenly into a 9-inch, freezer safe pie plate to form a crust. Use the flat bottom of a small glass or dry measuring cup to create a tightly packed crust on the bottom and up the sides of the pie plate.

Bake the crust for 10 minutes. Remove from the oven and allow the crust to cool completely on the counter while you prepare the grasshopper pie filling.

To a large, 3 quart saucepan on medium heat, add the whole milk. Warm the milk for 2-3 minutes or just until the milk starts to steam and bubbles start to form around the edges of the saucepan. Do not bring the milk to a boil. Be sure to stir the milk often to prevent it from burning.

Add the marshmallows to the hot milk. Using a rubber spatula or wooden spoon, stir the marshmallows in the hot milk until they are completely melted and no lumps from the marshmallows remain. Remove the saucepan from the heat and allow the marshmallow mixture to cool completely to room temperature, while stirring often, before adding the rest of the ingredients.

To a large mixing bowl, add the very cold heavy cream. Beat the cream using a handheld mixer on medium-high speed, for 2-3 minutes or until stiff peaks form. Set aside.

To the cooled marshmallow mixture, add the green creme de menthe liqueur and clear creme de cacao. Stir to fully incorporate. Add the green food coloring drops (if using them) and stir until the mixture is smooth and uniform in color.

Slowly add the cooled marshmallow mixture to the whipped cream and gently fold the mixture to fully incorporate the marshmallow, being careful not to deflate to whipped cream too much. Fold until no white streaks remains and the grasshopper pie filling is smooth and fluffy.

Pour the grasshopper pie filling into the cooled chocolate pie crust and smooth the top to an even layer.

Garnish with the roughly crushed chocolate cookie crumbles.

Freeze the grasshopper pie for a minimum of 4 hours or up to overnight. You want the filling to be very firm and fully set up before slicing and serving.