Preheat the oven:
Set your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat.
In a medium bowl, whisk together: 1 ½ cups all-purpose flour, ½ teaspoon salt, 1 teaspoon baking soda, ½ cup unsweetened cocoa powder. Set aside.
Cream the butter and sugars:
In a large bowl, beat together: ¾ cup softened butter, ½ cup brown sugar and ½ cup granulated sugar. Mix until light and fluffy.
To the creamed butter mixture, add: 1 egg, 1 tablespoon milk and 1 tablespoon vanilla extract. Mix well until smooth and combined.
Gradually add the dry ingredients to the wet mixture, mixing just until incorporated. Don’t overmix.
Fold in Reese’s Pieces:
Stir in 1 cup of Reese’s Pieces, saving a few to press on top of each cookie before baking if desired.
Scoop dough into tablespoon-sized balls and place them 2 inches apart on the prepared baking sheet.
Bake for 7–9 minutes, or until the edges are set and the centers look slightly soft.
Allow cookies to cool on the pan for 2–3 minutes, then transfer to a wire rack to cool completely.
