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 butter pieces. Stir constantly until completely melted and smooth.
03 - Remove the saucepan from heat and stir in the vanilla extract until fully incorporated.
04 - Immediately pour the fudge mixture into the prepared baking pan, using a spatula to smooth the top into an even layer.
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 set and firm to the touch.
07 - Lift the fudge out of the pan using the parchment paper overhang. Place on a cutting board and slice into 25 even squares. Serve chilled or at room temperature.