In a great big glass bowl (or any microwave safe bowl), mix the melted butter, egg, brown sugar, vanilla and peanut butter. Whisk Together until combined.
Whisk in the flour, but do not overbeat the batter.
Pour batter into the pie dish.
Press the peanut butter cups into the batter. I pushed mine halfway down. Repeat with the peanut butter M&Ms.
Bake 28-30 minutes. To check for doneness, insert a toothpick and it should come out with just a few crumbs or nothing at all.
Cool and eat.
Notes
Recipe from Averie Cooks
Recipe by Whisk Together at https://www.whisktogether.com/2015/05/07/peanut-butter-pie/