Preheat the Oven: Begin by preheating your oven to 350°F (175°C) while you prepare the cookie dough.
Mix Wet Ingredients: In a large mixing bowl, combine the peanut butter, sugar, egg, vanilla extract, and baking soda. Use a hand mixer or spatula to mix until completely smooth.
Incorporate Reese's Pieces: Gently fold in one cup of Reese's Pieces. This is where the fun begins as you add those colorful bits to the dough!
Scoop and Shape: Using a cookie scoop or tablespoon, drop dough balls onto a parchment-lined baking sheet, spacing them about two inches apart. You can gently press additional Reese's Pieces on top for presentation.
Bake: Place the baking sheet in the preheated oven and bake for 10-12 minutes until the edges are set but the centers remain soft.
Cool: Let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.