Ingredients
Cookies:
1 1/4 cups all-purpose flour
1 1/2 cups old-fashioned oats
1/2 teaspoon baking soda
1/2 teaspoon salt
1/2 teaspoon ground cinnamon
1/2 cup (8 tablespoons) unsalted butter, at room temperature
3/4 cup packed light brown sugar
1 large egg, at room temperature
1 teaspoon vanilla extract
Filling:
1/2 cup (8 tablespoons) unsalted butter, at room temperature
1 7-oz container marshmallow creme
2 cups confectioners’ sugar
1 teaspoon vanilla extract
Preparation
Preheat oven to 375 F. Line a baking sheet with parchment paper.
In a medium bowl, whisk the flour, oats, baking soda, salt and cinnamon together. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and brown sugar on medium speed until light and fluffy, about 4-5 minutes. Add the egg and vanilla and beat to combine. Add the dry ingredients to the mixer in 3 additions, beat just until combined.
Use a small cookie scoop to portion the dough into approximately 1 tablespoon balls. Place them on the prepared baking sheet, leaving about 1 1/2-2 inches between them. Bake for 9-10 minute, or until the edges of the cookies are golden brown and set (the middles may still seem a little underdone - they’ll set up as they cool). Transfer the baking sheet to a wire rack and let the cookies cool for a few minutes then remove them to the rack to cool completely.
To make the filling: In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and marshmallow creme on medium speed until smooth and fluffy, about 3 minutes. Add the confectioners’ sugar in 2 additions then add the vanilla and continue beating until the filling is smooth and thick.
Match the cookies in pairs by size. Transfer the filling to a piping bag and pipe about 1 tablespoon onto the flat side of one cookie of each pair. Sandwich the cookies together, and press the filling to the edges.
