1. Ensure butter is at room temperature. Partially crush M&Ms in a plastic bag. Chop Reese’s trees into bite-sized pieces and place in the fridge to firm up.

2. In a large bowl, use a spatula to combine the soft butter and brown sugar until thoroughly mixed with no butter streaks. Add the egg and vanilla; mix for 1–2 minutes until the mixture lightens slightly.

3. Add the flour, baking soda, and salt to the wet mixture. Combine slowly and carefully until just combined. Do not overmix.

4. Reserve a handful of crushed M&Ms and chopped Reese’s. Add the remaining candy to the dough and fold in. Cover the dough tightly with plastic wrap and chill in the fridge for at least 1 hour (up to 12 hours).

5. Remove the chilled dough. Using a scoop, portion out 10 cookies. Gently press the reserved M&Ms and chopped Reese’s onto the tops of the dough balls, then lightly flatten the tops with your palm.

6. Preheat oven to 350°F (175°C). Place the cookie sheets back in the fridge while the oven preheats. Bake for 10–12 minutes until the edges are golden and centers are slightly soft.

7. Allow cookies to cool on the sheet for 5 minutes before transferring to a wire rack to cool completely. Enjoy!