Step 1

Add butter, milk, semi-sweet chocolate chips, bittersweet chocolate chips and marshmallows to a large saucepan.

Step 2

Heat over low heat, stirring constantly until chocolate and marshmallows have melted (it will take a while for the marshmallows to melt, keep stirring).

Step 3

Remove from heat, stir in vanilla pour into a large mixing bowl and let cool, about 45 - 60 minutes (it should be about room temperature).

Step 4

Whip 1 3/4 cups heavy cream (preferably in a chilled bowl) until very stiff peaks form. Fold into cool chocolate mixture.

Step 5

Pour chocolate mixture into Oreo crust and spread into an even layer (if you don't want it as tall as mine is you can just reserve some of the mousse chilled in cups for later).

Step 6

Chill in refrigerator 3 hours.

Step 7

For the topping, whip remaining 1 cup cream with sugar (preferably in a cold mixing bowl) using an electric hand mixer until stiff peaks form.

Step 8

Spread over pie, garnish with chocolate then cut into slices. Store pie in refrigerator.

Step 9

*I've also made this successfully with 1 cup milk chocolate chips and 1/2 cup semi-sweet chocolate chips for more of a milk chocolate flavor vs. the regular dark chocolate flavor it has.

Step 10

**To make chocolate shavings just run a vegetable peeler down the sides of a bar of chocolate.