Crust:
1 cup chocolate or regular graham cracker crumbs
2 tablespoons brown sugar
3 tablespoons butter
Filling:
12 oz cream cheese, room temperature
2/3 cup brown sugar
2 large eggs
1/3 cup creamy peanut butter
1 tablespoon all-purpose flour
1/2 teaspoon vanilla
1/2 cup chocolate chips, melted (semisweet or milk chocolate)

Combine crumbs with brown sugar; mix in melted butter until well moistened. Pat into a 7-inch springform pan.

In a medium-sized mixing bowl, with an electric hand-held mixer, cream together the cream cheese and 2/3 cup brown sugar.Add eggs and beat on medium speed for about 2 minutes. Add peanut butter, flour, and vanilla; beat about 2 more minutes. Pour all but about 1/2 cup of the batter into the prepared pan. Combine the melted chocolate chips with the remaining batter and pour on top of the batter in the pan. Cut the chocolate batter in gently with a knife to make a swirling pattern, without disturbing the crust. Place on a rack or aluminum foil ring (to keep the pan off the bottom of the pot) in the crockery cooker. Cover and cook on high for 2 1/2 hours. Turn heat off and leave for about 1 1/2 to 2 hours, until cooled enough to remove. Cool completely before removing from pan. Chill before serving, and store leftovers in the refrigerator.