Preheat oven to 350 degrees F. Grease mini muffin tins.
In a small bowl, whip butter and sugar until combined and
creamy. Beat in flour until mixture becomes crumbly, but evenly moist.
Scoop rounded teaspoonsful and form into a ball. Press into the bottom of each muffin cup and halfway up the side.
Combine chocolate chips and peanut butter chips in a bowl and stir until combined. Place 5 of the mixed chips in each
In a medium bowl, beat eggs, sweetened condensed milk, and vanilla extract until combined. Fill each mini-muffin
cup almost to the top with the egg mixture.
Bake until centers are puffed up and edges begin to brown, about 15 to
18 minutes. Remove to wire racks. (Centers will sink as they cool.) While the cups are still warm, sprinkle tops with remaining
mixed chocolate and peanute butter chips. The chips will retain their shape as they soften. Let cookie cups cool
completely before storing.