1. Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. In a large bowl, cream together the peanut butter, unsalted butter, granulated sugar, and brown sugar until light and fluffy, about 3 minutes.
3. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
4. In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
5. Gently fold in the chopped mini peanut butter cups and optional nuts, if using. Be careful not to overmix.
6. Using a tablespoon, drop rounded scoops of dough onto the prepared baking sheets, spacing them about 2 inches apart.
7. Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden. The centers should still be soft.
8. Remove from the oven and let the cookies cool on the baking sheets for 5 minutes before transferring to wire racks to cool completely.

As you bake these cookies, remember that it’s okay if they seem slightly underbaked when you first take them out. They will continue to set as they cool, resulting in that perfect chewy texture.