12marshmallow Peepsany colors, chopped/cut into 3-4 pieces each
Preheat oven to 350ºF. Line an 8" baking pan with foil, leaving an overhang over the sides. Spray with non-stick spray. Set aside.
In a small bowl, mix together flour, baking powder, baking soda, and salt. Set aside. In a medium bowl, whisk together the melted butter, brown sugar, vanilla, and egg until smooth.
Slowly add flour mixture and stir together until just combined. Fold in m&m's. The batter will be quite thick, but this is ok. Spread evenly into baking pan with a spatula. The layer of batter will look very thin, but it will puff up substantially during baking.
Bake blondies for 15 minutes. While the blondies are baking, chop or cut the Peeps. After the 15 minutes, remove the pan from the oven and, working quickly, spread the Peeps evenly over the surface of the blondies. Bake an additional 5 minutes, watching the Peeps closely so as not to burn them. Allow to cool completely before lifting foil out of pan and cutting into squares. Using a sharp knife that has been dampened with water will help in cutting through the marshmallow layer. Pull knife out from the sides when you cut as opposed to lifting the knife out of the cut. Blondies will stay fresh covered at room temperature for up to 5 days.