01 - Line an 8x8-inch 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 completely melted and smooth, about 8 to 10 minutes.
03 - Remove the saucepan from heat and quickly stir in the pure vanilla extract until fully incorporated.
04 - Pour the melted fudge mixture into the prepared baking pan and smooth the top evenly using a spatula.
05 - Immediately scatter the holiday sprinkles over the surface, gently pressing them in so they adhere to the fudge.
06 - Refrigerate the fudge for at least 2 hours, or until completely firm and set.
07 - Lift the fudge out of the pan using the parchment paper overhang. Cut into 24 even squares using a sharp knife. Serve chilled or at room temperature.