Chocolate Peanut Butter Whoopie Pies

Why I Love This Recipe
I'm always trying to invent something. Occasionally, it works out. My daughter's boyfriend adores the chocolate and peanut butter combination and this is what I came up with for him. Unfortunately, the pics are on my other computer and I haven't gotten the wireless connection to work yet, so they will come later.
Ingredients You'll Need
1 box (19.5 oz) traditional fudge brownie mix
1/2 cup unsalted butter, softened, divided
1 large egg
1 1/3 cups flour
1/2 cup buttermilk (may substitute sour milk)
1/2 cup peanut butter
1 cup powdered sugar
1 jar (7 oz) marshmallow cream
Directions
Preheat oven to 350 degrees F.
Line cookie sheets with parchment paper.
In large bowl, combine brownie mix, 1/4 cup butter and 1 egg. Beat until just combined.
Alternate adding flour and buttermilk and continue to beat until well-blended.
Drop rounded teaspoons of batter, 2 inches apart, onto cookie sheets.
Bake for 9-11 minutes or until cookies are dry to the touch and firm.
Let cookies set on cookie sheet for at least 5 minutes before removing to wire rack. Cool comletely.
In medium bowl, cream 1/4 cup butter and peanut butter.
Add powdered sugar and beat until smooth.
Add marshmallow cream and beat until fluffy.
Spread filling between the flat sides of two cookies to make a sandwich.
Wrap each whoopie pie individually in plastic wrap.