01 - Line an 8x8-inch baking pan with parchment paper, leaving enough overhang on the sides to easily lift the fudge out once set.
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, about 5 to 7 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 use a spatula to smooth the top into an even layer.
05 - Immediately scatter the holiday sprinkles evenly across the surface, gently pressing them down so they adhere to the fudge.
06 - Refrigerate the fudge for at least 2 hours, or until it is completely firm to the touch.
07 - Lift the fudge slab out of the pan using the parchment paper overhang. Place on a cutting board and cut into 24 even squares using a sharp knife. Serve chilled or at room temperature.