In a bowl, add the butter and brown sugar, and stir to combine.
2. Step
Add the egg and mix until fully incorporated.
3. Step
Stir in the peanut butter and vanilla.
4. Step
Add the flour, salt, and baking soda.
5. Step
Gently fold in the peanut butter cups.
6. Step
Chill dough for at least 1 hour.
7. Step
Preheat oven to 350˚F (180˚C).
8. Step
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. Step
Bake for 8 to 10 minutes, until bottom edges of cookies are golden.
10. Step
Let cookies cool. Can be stored in an airtight container up to 5 days.
