Peanut Butter Chocolate Bars

1 pkg. plain yellow cake mix
1 stick melted butter
1 c. creamy peanut butter
2 eggs
1 (12 oz) pkg. chocolate chips
1 can sweetened condensed milk
2 T. butter
2 tsp. vanilla
1. Mix together cake mix, butter, peanut butter and eggs. Press this into a greased 9x13 pan and reserve 1 1/2 c. of mixture for the topping.
2. Melt chocolate chips, sweetened condensed milk and butter on low heat. Once melted remove from heat and add vanilla.
3. Spread chocolate mixture over the mixture pressed in the pan and then crumble the 1 1/2 of reserved cake mixture on top. Bake for 20-25 minutes at 325 degrees. Cool completely before cutting into bars.