Preheat the oven to 350°F. Butter an 8-inch springform pan and then line the bottom with parchment paper. Apply additional butter to the parchment paper and then dust bottom and sides with all-purpose flour.
Melt the chocolate, butter, and salt together in a medium-sized bowl in 30-second increments in the microwave stirring between until smooth. Stir in the vanilla and sugar and let cool slightly.
Add the eggs one at a time, whisking to combine after each addition. Fold in the flour until smooth and then add the peanut butter cup halves. Pour into the prepared pan.
Bake for 15 minutes. Place on a wire cooling rack to cool slightly.
Peanut Butter Cheesecake - Prepare while brownie layer is baking
Reduce the oven temperature to 300° after the brownie layer is baked.
In the bowl of an electric mixer fitted with the whisk attachment, combine cream cheese and granulated sugar. Whip until smooth and creamy. Add the peanut butter, cornstarch, salt, and vanilla. Beat until smooth and creamy. Add the eggs one at a time, mixing after each addition.
Wrap the outside of the springform pan tightly with two layers of aluminum foil to assure that it's completely sealed. Pour the Peanut Butter filling into the pan. Place a larger pan into the oven and fill the bottom with very hot water. Place the springform pan in the water bath. Add enough water to assure that the water comes up to the middle of the springform pan. Bake 60 to 70 minutes. until the cheesecake is set but slightly jiggly in the middle when you shake it gently.
Turn the oven off and let the pan sit in the oven for 15 minutes with the door ajar. Cheesecake will continue to finish cooking and it helps prevent cracking.
Remove the cheesecake from the oven and the water bath, and let cool completely; this can take up to 4 hours. Gently loosen the cheesecake from the pan and place it on a plate. If cake sticks, gently loosen it with a thin knife. Cover the cheesecake and refrigerate at least 8 hours or overnight.
Combine the semi-sweet chocolate, cream, and salt in a microwave-safe bowl. Heat in 30-second intervals stirring in between until smooth. Allow mixture to cool until it thickens into a spreadable consistency. It's o.k. to cool it in the refrigerator, stirring occasionally.
Peanut Butter Glaze
Melt the butter, salt, and peanut butter together in a microwave-safe bowl in 30-second intervals stirring in between. Add the powdered sugar and mix until smooth. The glaze will thicken as it cools.
Spread the chocolate ganache along the sides of the chilled cheesecake and spread the peanut butter glaze over the top. Garnish with additional peanut butter cups.
This recipe was calculated using the exact brands and measurements I used to make this recipe. If you are following a strict diet please note changing anything will cause the nutritional info to change. My calculations are intended as a guide only.