Step 1

Preheat oven to 350°F (177°C). Combine the Oreo crumbs and melted butter together in a medium bowl. Press tightly into the bottom and up the sides of an ungreased 9-inch pie dish. Bake for 18 minutes. Allow to cool completely. I do this the night before to save time!

Step 2

Microwave the chopped chocolate and butter together in a large heat-proof bowl, stopping and stirring every 15 seconds until completely melted. Set aside.

Step 3

Place egg whites, sugar, and cream of tartar in a heatproof bowl. Set bowl over a saucepan filled with two inches of simmering water. Do not let it touch the water. (You can use a double boiler if you have one.) Whisk constantly until sugar is dissolved, about 4 minutes. Transfer the mixing bowl to an electric mixer fitted with a whisk attachment. Beat on high speed for 5-6 minutes until soft, glossy peaks form. See photo above for a visual. Gently fold mixture into the chocolate. Wash the mixer bowl and whisk attachment clean.

Step 4

Using a handheld or stand mixer fitted with a whisk attachment, beat the 2 cups of heavy cream on high speed until stiff peaks form, about 4-5 minutes. Gently fold whipped cream into the chocolate/egg white mixture. Do not overmix; it will deflate the mousse. (No need to wash or wipe the bowl/whisk attachment clean– you’ll make sweetened whipped cream in step 6.)

Step 5

Spread 1/2 of the mousse into cooled pie crust. Top with Oreo crumbs. (The 6 whole Oreos crushed into crumbs!) Top with remaining chocolate mousse, mounding in the center to create a dome shape. Place in the refrigerator for 5 minutes as you prepare the whipped cream topping.

Step 6

Using a handheld or stand mixer fitted with a whisk attachment, beat the 1 cup of heavy cream, granulated sugar, and vanilla on high speed until slightly stiff peaks form, about 4 minutes. You want the peaks to be somewhat soft so the whipped cream spreads nicely on the mousse. Remove pie from the refrigerator and spread whipped cream on top—once again keeping that dome shape in the center.

Step 7

Top with chocolate shavings, if using. Refrigerate pie uncovered for at least 4-5 hours or overnight. Slice and serve. Usually the 1st slice isn’t as beautiful as the 2nd! It’s easier to cut after you have 1 slice out.