Spray an 8X8 baking pan with cooking spray, then line the bottom with waxed paper or parchment paper.
Place the white chocolate chips and peanut butter in a large mixing bowl (microwave safe bowl).
Heat in the microwave in 30-second intervals, stirring after each interval, until the white chocolate chips and peanut butter are melted, fully combined and smooth. Then stir in the sweetened condensed milk until fully combined.
Pour the mixture into the prepared 8X8 baking dish. Refrigerate until the fudge is set (approximately 2-3 hours).
Once the fudge is fully set, cut into pieces and serve!