DIRECTIONS

In a microwave, melt butter and unsweetened chocolate; set aside. In a mixing bowl, beat brown sugar and eggs until light and fluffy, about 4 minutes. Add chocolate mixture and vanilla; mix well. Combine flour and baking powder; add to batter. Stir in chopped chocolate. Spread 1 cup into a greased 9-in. springform pan. Cover and refrigerate remaining batter. Place pan on a baking sheet. Bake at 350° for 17-19 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack for 5 minutes; place in freezer for 15 minutes.
    For filling, in a mixing bowl, beat peanut butter, cream cheese and brown sugar until smooth. Add eggs and sour cream; beat on low speed just until combined. Spread remaining brownie batter about 1-1/2 in. high around sides of pan, sealing to baked crust. Pour filling into center. Bake at 350° for 45 minutes or until center is almost set.
    For topping, combine sour cream and sugar; spread over filling to within 3/4 in. of edges. Return cheesecake to the oven; turn oven off and let stand for 5 minutes. Cool on a wire rack for 10 minutes. Carefully run a knife around pan to loosen; cool 1 hour longer. Chill overnight. Remove sides of pan. Drizzle with melted chocolate. Refrigerate leftovers. Yield: 12 servings.