Mix butter, peanut butter, sugars, vanilla & eggs well.
In a separate bowl, combine dry ingredients. Incorporate into wet mixture.
Refrigerate 1 hour, when possible.
Preheat oven to 375 degrees.
Grease your oven safe baking dish. Press in a thin layer of cookie dough.
Add marshmallows & peanut butter cups, sprinkle cookie dough & brown sugar on top.
Bake 15 minutes. Serve warm.