Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.
In a large mixing bowl, combine the creamy peanut butter, granulated sugar, and light brown sugar. Mix until smooth and creamy.
Add the egg and vanilla extract to the peanut butter mixture and beat until fully incorporated.
In a separate bowl, whisk together the baking soda, salt, and all-purpose flour.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chopped Reese’s peanut butter cups evenly throughout the dough.
Using a tablespoon or cookie scoop, drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Optional: Gently press the tops of each cookie with a fork to create a crisscross pattern.
Bake the cookies in the preheated oven for 10 to 12 minutes, or until the edges are lightly golden but the centers remain soft.
Remove the cookies from the oven and allow them to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.