1 ½cups(318g)lightly packed light or dark brown sugar
1large egg
1teaspoonvanilla extract
1teaspoonbaking soda
½teaspoonground cinnamon, optional
½teaspoonsalt
1 ¼cups(178g)all-purpose flour
3cups(300g)quick oats (see note for using rolled oats)
Filling:
¾cup(170g)salted butter, softened
1 ½cups(171g)powdered sugar
1 (7-ounce)jarmarshmallow fluff/creme
1teaspoonvanilla extract
1 to 2tablespoonsheavy cream
Instructions
Preheat the oven to 350 degrees F. Line a couple baking sheets with parchment paper. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment or using a handheld electric mixer, combine the butter, brown sugar, egg, vanilla, baking soda, cinnamon (if using) and salt and mix until light and fluffy, 2-3 minutes, scraping down the sides of the bowl as needed.
Add the flour and oats and mix until no dry streaks remain.
Scoop the cookie dough into balls (I use a #40 medium cookie scoop - about 2 tablespoons of dough per cookie, but you can make them smaller or larger depending on how big you want the finished cream pies), roll lightly for a uniform round shape, and place several inches apart on the prepared baking sheets.
Bake for 8-10 minutes until set around the edges but still soft in the center. You don't want to overbake these cookies! Let the cookies sit for a few minutes on the baking sheet before removing to a wire rack to cool completely. Repeat with remaining cookie dough. *These are meant to be a relatively flat, chewy, super soft cookie; however, if your cookies are spreading too much still, increase baking temperature to 375 degrees, bake on convection (at 350 degrees) or add a couple tablespoons more flour to the dough.*
For the filling, with an electric mixer (stand mixer or handheld) whip together the butter, powdered sugar, marshmallow fluff and vanilla until very thick and creamy, 2-3 minutes. Add heavy cream, as needed, to thin to a fluffy, spreadable consistency.
Spread a couple tablespoons of filling on the bottom of half of a cookie and top with an unfrosted cookie (bottom sides together). Repeat with remaining cookies.
Notes
Oats: this recipe works best with quick oats. You can experiment using old-fashioned rolled oats (the texture will be much more oat-y and the cookies may spread a bit more); or you can pulse old-fashioned oats in a blender or food processor until coarsely chopped similar in texture to quick oats.Filling: I've also used a simple, homemade vanilla frosting for the filling instead of the recipe above calling for marshmallow fluff. The marshmallow fluff recipe gives a flavor/creaminess boost that better mimics the storebought cookies (in a much, much better way), but both options are delicious.Make Ahead: these keep well in the refrigerator for several days (keep them well covered). The unfilled cookies freeze great; I haven't tried freezing them once they have been filled with frosting.