01 - Line an 8-inch square baking pan with parchment paper, leaving an overhang on the sides for easy removal.
02 - In a medium saucepan over low heat, combine the semi-sweet chocolate chips, sweetened condensed milk, and unsalted butter. Stir constantly until the mixture is completely melted and smooth.
03 - Remove the saucepan from the heat and stir in the vanilla extract until fully incorporated.
04 - Immediately pour the fudge mixture into the prepared baking pan, smoothing the top evenly with a spatula.
05 - Sprinkle the holiday sprinkles evenly across the surface of the fudge, gently pressing them in so they adhere.
06 - Refrigerate the fudge for at least 2 hours, or until it is fully firm and set.
07 - Once set, lift the fudge out of the pan using the parchment overhang. Cut into 25 even squares and serve.