1. In a bowl, add the butter and brown sugar, and stir to combine.
2. Add the egg and mix until fully incorporated.
3. Stir in the peanut butter and vanilla.
4. Add the flour, salt, and baking soda.
5. Gently fold in the peanut butter cups.
6. Chill dough for at least 1 hour.
7. Preheat oven to 350˚F (180˚C).
8. Once dough is chilled, scoop out a ball about 2 inches (5 cm) wide. Place on a parchment paper-lined baking sheet, leaving about 2-inches (5 cm) in between each ball of dough.
9. Bake for 8 to 10 minutes, until bottom edges of cookies are golden.
10. Let cookies cool. Can be stored in an airtight container up to 5 days.
11. Enjoy!

Original recipe available HERE.