Prepare the Pan:

Line an 8x8-inch baking pan with parchment paper or wax paper, leaving a little overhang to help lift the fudge out once set. Set aside.

Melt the Butter and Peanut Butter:

In a medium saucepan over low heat, melt the butter and peanut butter together. Stir occasionally until smooth and combined, about 2–3 minutes.

Add Powdered Sugar:

Once the peanut butter and butter mixture is smooth, remove from heat and gradually stir in the powdered sugar. Mix until fully incorporated, making sure there are no lumps.

Add Vanilla:

Stir in the vanilla extract until evenly mixed.

Pour and Chill:

Pour the peanut butter mixture into the prepared baking pan, spreading it out evenly with a spatula. If you’re using chocolate chips, sprinkle them on top and gently press them into the fudge. Refrigerate the fudge for about 2–3 hours, or until firm.

Cut and Serve:

Once the fudge is set, lift it out of the pan using the parchment paper overhang. Cut into small squares and serve.