Chocolate Pistachio Cheesecake

Step 1
Preheat the oven to 325 degrees F (165 degrees C). Coat a 9-inch springform pan with cooking spray.

Step 2
In a food processor, pulse cookies, 1/4 cup pistachios, and 2 tablespoons sugar until mostly finely ground. (It's OK to leave some texture.) Add melted butter; pulse to combine. Spread mixture evenly in the prepared pan and press firmly into bottom of pan.

Step 3
For pistachio butter, blend remaining 1/2 cup pistachios in a small food processor until very smooth and slightly loose consistency, about 5 minutes. Transfer pistachio butter to a large bowl; add cream cheese, avocado, 1 cup yogurt, cornstarch, and 3/4 cup white sugar. Beat with an electric mixer at medium speed just until mixture is nearly smooth. Add egg whites, almond extract, and a pinch of salt; beat until just combined. Spread over prepared crust.

Step 4
Bake until surface near edges appears set when gently wiggled, about 40 minutes. Turn off oven. Let cheesecake stand in oven 30 minutes. Cool in pan on wire rack 15 minutes. Using a thin metal spatula, loosen cheesecake from sides of pan. Cool completely.

Step 5
For mousse, beat whipping cream, powdered sugar, vanilla, remaining 1 cup yogurt and a pinch salt in a bowl with an electric mixer at medium-low speed until fluffy, about 4 minutes. Spread over cheesecake.

Step 6
Spread whipped topping over mousse. Chill, covered, at least 4 hours or up to 5 days. To serve, remove from pan, slice, and garnish with additional whipped topping and pistachios.