Preheat the Oven:
Preheat your oven to 325°F (165°C). Line a 12-cup muffin tin with paper cupcake liners.

Prepare the Crust:
In a medium bowl, combine the graham cracker crumbs, sugar, and melted butter. Mix until the crumbs are fully coated.
Spoon about 1 tablespoon of the crust mixture into each muffin cup. Use the back of a spoon to gently press it down. Bake the crust for 5-7 minutes, then remove from the oven and set aside to cool.

Make the Cheesecake Filling:
In a large bowl, beat the softened cream cheese and peanut butter together until smooth and creamy, about 2 minutes. Add the powdered sugar and vanilla extract, and mix until fully combined.
Add the eggs, one at a time, mixing well after each addition. Be careful not to overmix. The batter should be smooth and thick.

Assemble the Mini Cheesecakes:
Evenly distribute the cheesecake batter over the cooled crusts in the muffin tin, filling each cup about ¾ full.
Gently tap the muffin tin on the counter to level the batter.

Bake:
Bake the mini cheesecakes for 18-20 minutes, or until the edges are set, and the centers are slightly jiggly. Turn off the oven and let the cheesecakes cool in the oven with the door slightly ajar for 1 hour.

Chill:
After the cheesecakes have cooled, transfer the muffin tin to the fridge and chill for at least 3 hours, or overnight for best results.

Add the Toppings:
Once chilled, top each cheesecake with a chopped mini peanut butter cup.

Serve:
Remove the cheesecakes from the muffin tin and enjoy! For extra indulgence, drizzle with chocolate or peanut butter sauce before serving.