Add butter to a medium saucepan and melt over low heat. Once melted, add the white chocolate chips to the saucepan and stir to avoid the chocolate from burning.
Once the chocolate is melted and smooth, add the sweetened condensed milk and stir until combined. Add the sugar cookie mix and stir until the mix is incorporated. The fudge should be thick, smooth and stir-able.
Remove from heat and stir in the holiday sprinkles. Pour the fudge into a parchment paper lined 8x8 (or 9x9) pan and smooth it out so it is distributed evenly.
Add about 8 drops of food coloring to you fudge and use a spoon to swirl the colors into the fudge. Make sure not to swirl too much of the colors won't blend well.
Cover and let set in the fridge for at least 4 hours, preferably overnight. When ready to serve slice into squares and enjoy!
Leftover Storage: Store leftover homemade fudge in an airtight container in the fridge for up to 3 weeks. Fudge will stay fresh at room temperature for up to 1 week.
Freezing Christmas Fudge: You can freeze this fudge for up to 3 months! Wrap each piece of set fudge in cling wrap, then foil and place in a freezer bag. Let thaw in the fridge or at room temperature to soften up a bit when ready to enjoy.
Perfect for any Holiday: Customize this holiday fudge with different sprinkles and colors to fit any theme or holiday.