Yellow cake mix
2 eggs
1/2 stick butter
1 c. peanut butter

Mix together. Spread 3/4 of batter into 9 x 13 inch greased pan.

FILLING:

6 oz. chocolate chips
14 oz. can sweetened condensed milk
2 tbsp. butter

Melt together. Pour filling on batter. Spread. Drop rest of batter on top. Bake at 350 degrees for 30 minutes.