Preheat oven to 350?F.
Lightly grease 8x8-inch pan.
In medium bowl, stir together cookie mix, butter, egg, and 1/2 cup chocolate chips.
In separate bowl, blend peanut butter and sweetened condensed milk.
Press half of cookie dough into prepared pan.
Spread molten chocolate filling over dough.
Top with peanut butter mixture.
Crumble remaining cookie dough over peanut butter layer and top with remaining chocolate chips.
Bake 36-40 minutes or until center is set.