1. The night before you make this mousse, place 14 mint Oreos in a large mixing bowl and cover them with the heavy cream. Cover the bowl with plastic wrap and place the bowl in the fridge.
2. In the bowl of a stand mixer fitted with the whisk attachment, or using a handheld mixer, whip the contents of the mixing bowl on high, along with the powdered sugar and mint extract (if using), until the mixture is light and fluffy.
3. Crush the remaining 7 Oreos in a bag, using a rolling pin, or in your food processor. Divide the crushed crumbs among 4 different serving dishes then add the whipped mousse on top of the dish, dividing it up equally. Serve immediately, or place a lid on the dish (or using plastic wrap) and refrigerate the mousse for a few hours. Top with whipped cream and additional mint Oreos, if desired!

Mousse will keep in the fridge, covered, for 3-4 days.