Step 1

Line an 8x8-inch pan with a parchment paper or aluminum foil sling for easy removal and cutting once the fudge is set. If using aluminum foil, be sure to butter it so the fudge will come off easily.

Step 2

Combine the brown sugar, milk, and butter in a medium saucepan over medium-high heat. Cook while stirring frequently until the brown sugar and butter dissolve and the mixture comes to a boil.

Step 3

Boil for 2 minutes.

Step 4

Remove from heat and stir in the peanut butter and vanilla until smooth and combined.

Step 5

Add the powdered sugar to a large, heat-safe bowl, then pour the hot peanut butter mixture over it. Beat together with a hand mixer until combined and there are no lumps of powdered sugar remaining, then transfer the fudge to the prepared pan. Let set at room temperature for about 3 hours until set up before slicing into squares.

Step 6

Store in an airtight container on the counter or in the fridge for up to 1 week.