Make the Fudge Mixture
Combine the sugar cookie mix, white chocolate chips, and sweetened condensed milk in a medium saucepan over medium-low heat. Stir constantly until the chocolate melts and the mixture becomes smooth, thick, and creamy.
Microwave Method
Add the white chocolate chips and sweetened condensed milk to a microwave-safe bowl and heat in 20–30 second intervals, stirring between each. Once the chocolate is mostly melted, add the sugar cookie mix and stir until the fudge mixture is completely smooth. Keep intervals short to prevent scorching.
Prepare the Pan
Line an 8x8 or 9x9 baking pan with parchment paper, trimming the corners so it fits flat. Spray lightly with cooking spray or non-stick spray for extra easy removal.
Pour and Add Sprinkles
Pour the fudge mixture into the prepared pan and smooth the top with a spatula. Add festive sprinkles or Christmas sprinkles over the surface. Lay a sheet of plastic wrap on top and gently press so the sprinkles adhere without melting or bleeding into the fudge.
Chill and Cut
Let the fudge cool at room temperature, then refrigerate for 2–3 hours until firm. Lift the slab from the pan using the parchment overhang. Transfer to a cutting board and cut into 36–39 squares with a sharp knife for clean, crisp edges.
Package for Gifting
Place a few pieces in cellophane bags, tie with a ribbon or Christmas string, and you’ve got a festive, budget-friendly great edible gift for friends, neighbors, or teachers.