Disappearing Marshmallow Bars

I remember my mom making these when I was very little and watching the marshmallows puff up in the oven.  Weird thing to remember, but they are so good.

2 cups flour
2 tsp. baking powder
1/2 tsp. salt
1 cup butterscotch pieces
1/2 cup butter
2/3 cup brown sugar
1 tsp. vanilla
2 eggs
1 cup chocolate chips (I prefer semi sweet in this recipe)
2 1/2 cups mini marshmallows


Put flour, baking powder and salt into a bowl and set aside.
Heat in a sauce pan until melted; butterscotch pieces and butter. Remove from heat.
Add brown sugar, vanilla and eggs to butter mixture.  Beat well.  Add flour mixture slowly.  Then add chocolate chips and marshmallows.  Spread into a greased jelly roll pan.  Bake in a pre heated 350 degree oven for 15-18 minutes.
(I put mine in a 13x9 inch pan.  It just makes them a little gooey-er.  You will have to bake them for a couple more minutes too.)
They are so yummy I could seriously eat the whole pan!