Ingredients

For the crust
• 9 oz (1 package) Nabisco chocolate wafers
• 1 cup semisweet chocolate chips
• 1/2 cup dark brown sugar, firmly packed
• 7 tablespoons unsalted butter, melted
For the fudge
• 1 cup heavy whipping cream
• 13 ounces semisweet chocolate, chopped
• 2 tablespoons smooth peanut butter
For the cheesecake
• 2 8-oz packages full fat cream cheese, room temperature
• 1 1/4 cups smooth peanut butter
• 1 cup granulated sugar
• 3/4 cup full fat sour cream, room temperature
• 3 large eggs, room temperature
• 1 tablespoon vanilla extract
• 1/4 teaspoon kosher salt
For the ganache
• 1/3 cup heavy whipping cream
• 4 1/2 oz semisweet chocolate, chopped
• 1 tablespoon smooth peanut butter

Instructions

Prepare the pan
1. Cover the outside of a 9 inch springform pan with two layers of aluminum foil.
For the crust
2. Finely crush wafers in a food processor until they make fine crumbs. Add chocolate chips and brown sugar a pulse to combine. Add butter and continue pulsing until thoroughly moistened. (If you don't have a food processor, you can crush the cookies in a heavy duty ziploc bag using a rolling pin, then pour into a bowl and add the remaining ingredients).
3. Transfer the crumbs to the springform pan and press them up the sides of the pan almost to the top (within a half inch) and into the bottom of the pan to form the crust. Place in refrigerator to chill while you make the fudge.
Make the fudge
4. Bring heavy cream to a simmer in a saucepan. Remove from heat and add the chocolate and peanut butter, whisking until smooth. Pour into pan and spread into an even layer. Place in the freezer for about 30 minutes, until firm.
Make the cheesecake
5. Preheat the oven to 325°F
6. Using an electric mixer fitted with the paddle attachment, beat the cream cheese, peanut butter, and sugar until light and fluffy, scraping down the sides as needed.
7. Scrape down the sides and add the sour cream, beating to combine.
8. Add the eggs, one at a time, beating until incorporated.
9. Add vanilla and beat until incorporated, scraping down the sides and bottom to ensure everything is evenly mixed. Pour cheesecake over the fudge layer.
Bake in a water bath
10. Place foil-wrapped springform pan into a roasting pan large enough to hold it.
11. Fill the pan with enough hot water to come 1 inch up the side of the springform pan and transfer very carefully to the oven.
12. If you don't want to use a water bath, you can bake it without a water bath as well, but the water bath is more gentle. To bake without a water bath, simply place your springform pan onto a baking sheet in the oven. (The baking sheet will make it easier to remove when the cheesecake is done).
13. Bake the cheesecake for 75 to 90 minutes until the cake is mostly firm but will still jiggle a bit in the middle when poked. If you like to be more scientific, the center of the cheesecake should reach about 150-155°F on an instant read thermometer. The top will be a light golden brown.
14. When done, allow to cool about 30 minutes on a wire rack, then transfer to the refrigerator for at 3 hours (or longer).
Make the ganache
15. Heat cream in a small saucepan until simmering.
16. Remove from the heat and add the chocolate and peanut butter, whisking until smooth and shiny.
17. Pour onto the cheesecake and spread evenly across the top of the cheesecake.
18. Return cheesecake to fridge for at least 30 minutes, until the ganache has set.
Serve the cheesecake
19. Run a small offset spatula or butter knife around the outside of the cake to make sure it doesn't stick to the pan. Unhinge the sides to remove the bottom piece containing the cheesecake.
20. To cut the cheesecake, run a sharp knife under hot water and wipe with a warm damp cloth. Cut into thin slices, pressing firmly at the bottom to ensure you cut through the crust layer at the bottom, wiping the knife as needed.