Prepare an 8x8 inch baking dish by lining with parchment paper or tin foil. Spray lightly with cooking spray. Set aside.
In a saucepan, over medium low heat, combine the condensed milk, white chocolate chips, and peanut butter. Let cook until melted together and smooth. Remember to stir frequently so that it does not burn.
Once melted and smooth, add in 1 1/2 cups of the chopped Reese's and stir together.
Pour the fudge into your prepared pan and smooth out. It's easiest to use the back of a spoon. Gently press the remaining chopped Reese's on top.
Let refrigerate for 2-3 hours or until set and firm. Cut into small squares.
Store leftovers in the fridge. Fudge will soften up as it sits out at room temperature. It's yummy straight from the fridge or when it's been out and it's a bit softer. Both ways are delicious!