Ingredients:

  • 1 cup (2 sticks) unsalted butter, softened
  • 1 cup granulated sugar
  • 3/4 cup light brown sugar, packed
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 2 1/4 cups all-purpose flour
  • 3/4 cup unsweetened cocoa powder (Dutch-processed)
  • 1 teaspoon espresso powder
  • 1 teaspoon baking soda
  • 1/2 teaspoon salt
  • 1 1/2 cups semi-sweet chocolate chips
  • 1 cup mini marshmallows
  • Flaky sea salt, for finishing (optional)

Instructions:

  1. In a medium bowl, whisk together the flour, cocoa powder, espresso powder, baking soda, and salt. Set aside.
  2. In the bowl of a stand mixer, beat the softened butter, granulated sugar, and brown sugar until light and fluffy (about 3–4 minutes). Scrape down the sides.
  3. Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract.
  4. Gradually add the dry ingredient mixture to the wet ingredients on low speed, mixing just until combined. Do not overmix.
  5. Gently fold in the chocolate chips and half of the mini marshmallows using a spatula.
  6. Cover the bowl tightly with cling film and refrigerate the dough for a minimum of 1 hour (up to 24 hours) to prevent excessive spreading.
  7. Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
  8. Scoop dough balls (about 2 tablespoons each) onto the prepared sheets, leaving 2 inches between them. Gently press a few remaining mini marshmallows into the top centre of each dough ball.
  9. Bake for 10–12 minutes. Cookies should look set on the edges but still slightly puffy and underdone in the very centre.
  10. Immediately sprinkle a pinch of flaky sea salt over the hot cookies. Let them sit on the baking sheet for 5 minutes to firm up before transferring them to a wire rack to cool completely.