Banana Whoopie Pies with Peanut Butter Filling

2 cups flour
½ teaspoon baking powder
½ teaspoon baking soda
½ teaspoon salt
½ cup mashed banana (about 1 large banana)
½ cup sour cream
½ cup butter (1 stick)
½ cup granulated sugar
½ cup packed light brown sugar
1 large egg
½ teaspoon vanilla extract

Preheat oven to 350 degrees. Line 2 baking sheets with parchment paper.

Sift flour, baking powder, baking soda, and salt into a bowl. Combine banana and sour cream in another bowl. Beat butter, granulated sugar, and brown sugar with a mixer on medium-high speed until pale and creamy, about 3 minutes. Add egg and vanilla, beating until incorporated. Add flour mixture and banana mixture in alternating additions, beginning and ending with the flour mixture.

Transfer batter to a pastry bag fitted with a plain tip with a large opening. (I used a number 12). Pipe batter into 1-inch rounds, spacing 1 inch apart. Bake until edges are golden, about 12 minutes. Let cool a few minutes and then transfer cookies to a wire rack.

Peanut Butter Filling:

1 cup creamy peanut butter
1 stick butter
1 teaspoon vanilla
2 cups powdered sugar

Beat peanut butter, butter, and vanilla into a medium bowl. Beat in the powdered sugar, a little at a time, until mxture reaches desired consistency. There may be some sugar leftover.

To assemble cookies, spread or pipe filling onto the bottom of half the cookies. Top with the remaining cookies.