Fluffernutter Sandwich Cookies

for the cookies:
1/2 cup butter, softened
3/4 cup creamy peanut butter
1/2 cup sugar
1/2 cup brown sugar
1 egg
1/2 tsp vanilla
3/4 tsp baking soda
1/4 tsp salt
1 3/4 cups flour

for the marshmallow buttercream:
1 cup butter, softened
1 jar marshmallow creme
1 cup powdered sugar
1/2 tsp vanilla

Preheat oven to 350.
Combine the butter, peanut butter, sugar, brown sugar, egg, and vanilla.
Beat together until smooth, then mix in the flour, baking soda, and salt. 
Let the dough chill in the fridge for 15 minutes.
Use a small ice cream scoop to form the cookies.
Use the tines of a fork to make a crisscross pattern on the cookies.
Bake at for 8-10 minutes, or until the edges start to lightly brown.
Cool completely on a wire rack.
While the cookies are cooling, start on the marshmallow buttercream. 
Beat the butter, marshmallow creme, powdered sugar, and vanilla on high, until fluffy.
Spread the frosting on half of the cookies, then top with the remaining cookies.