Brownie Peanut Butter Cheesecake

From 201 Chocolate Treats

Crust
3 1/2 ounces semi-sweet chocolate, grated or finely chopped
1/4 C butter or margarine
1/2 C all-purpose flour
1/8 tsp baking powder
2 large eggs
1 C packed light-brown sugar
1 1/2 tsp chocolate extract
Filling
12 ounces cream cheese, room temperature
1 C packed light-brown sugar
3 large eggs
1/2 C sour cream or yogurt
1 1/3 C creamy peanut butter
Topping
3/4 C sour cream or yogurt
2 tsp granulated sugar
1/2 C creamy peanut butter

Position a rack in the center of the oven and preheat the oven to 350. Lightly grease and flour a 9 or 10" springform pan.
To make the crust, in the top of a double boiler over simmering water, melt 3 ounces of the chocolate and the butter, stirring until smooth. Remove from the heat.
Combine the flour and baking powder.
In a medium bowl, using an electric mixer on medium speed, beat the eggs until thick and light-colored. Beat in the brown sugar until well blended. Beat in the melted chocolate, chocolate extract, and remaining grated chocolate. Gradually stir in the dry ingredients, mixing just until blended. Spread 1 cup evenly onto the bottom of the prepared pan. Chill the remaining crust mixture.
Bake for 15-17 minutes, or until a cake tester inserted into the center comes out clean. Cool in the pan in the refrigerator 15-30 minutes.
To make the filling, in a large bowl, using an electric mixer on medium speed, beat the cream cheese and brown sugar until smooth. Beat in the eggs and sour cream. Beat in the peanut butter.
To prepare the pan, use a spatula to spread the remaining chilled crust mixture evenly around the insides of the pan. To make this easier, set the pan on its side and roll it, spreading at the same time. Pour in the filling mixture.
Bake 25-30 minutes, or until a cake tester inserted into the center comes out clean. Spread the topping on the cheesecake about 3 minutes before removing from the oven.
To make the topping, in a small bowl, using an electric mixer on medium speed, mix the sour cream, sugar, and peanut butter until smooth. Cool on a wire rack for 1 hour. Place in a plastic or paper bag and chill overnight.
Remove the side of the pan. Cut the cake into narrow wedges and serve.