Ingredients:

  • 1 cup (226g) unsalted butter, softened
  • 1 cup (200g) dark brown sugar, packed
  • 0.5 cup (100g) granulated white sugar
  • 1 large egg, room temperature
  • 2 tbsp (40g) unsulfured molasses
  • 2 tsp vanilla extract
  • 1.5 cups (190g) all-purpose flour
  • 3 cups (240g) quick-cooking oats
  • 1 tsp baking soda
  • 1 tsp ground cinnamon
  • 0.5 tsp sea salt
  • 0.5 cup (113g) unsalted butter, softened (for filling)
  • 1.5 cups (180g) powdered sugar, sifted (for filling)
  • 7 oz (198g) marshmallow crème
  • 1 tbsp heavy cream
  • 1 tsp vanilla extract (for filling)

Instructions:

  1. Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper or silicone mats.
  2. In a large bowl or stand mixer, beat 1 cup of softened butter with dark brown sugar and granulated sugar until pale and fluffy, about 2-3 minutes.
  3. Add the egg, molasses, and 2 teaspoons of vanilla extract to the butter mixture and beat until well combined.
  4. In a separate medium bowl, whisk together the flour, quick-cooking oats, baking soda, cinnamon, and sea salt.
  5. Gradually add the dry ingredients to the wet mixture on low speed until just combined. The dough will be thick and slightly tacky.
  6. Using a medium cookie scoop (approx. 2 tbsp), drop dough onto prepared baking sheets, spacing them 2 inches apart.
  7. Bake for 10 minutes until the edges are set but the centers still look slightly soft. Do not overbake. Cool completely on a wire rack.
  8. Prepare the filling: Beat 0.5 cup softened butter with powdered sugar, marshmallow crème, heavy cream, and 1 teaspoon vanilla extract until light and fluffy.
  9. Spread or pipe a generous amount of filling onto the flat side of one cooled cookie and top with a second cookie to create a sandwich.