Cream butter and sugars. Beat eggs in well.
Mix in peanut butter, sour cream, and vanilla.
Combine flour, baking powder, soda and salt together and add to creamed mixture.
Stir in most of the chocolate chips, reserving a few for the top.
Spoon mixture into a greased and floured 2 1/2 to 3-quart souffle dish
or mold (which will fit in your crock pot).
Place a small trivet in the crock pot, place the dish on the trivet,
then cover the dish with 4 layers of paper towels.
Cover loosely to allow steam to escape and cook on high for about 4 hours.
Test with a toothpick for doneness.
Cool in pot until dish is cool enough to handle,
then transfer to a wire rack to cool completely.