Prep the Pan: Line an 8x8-inch baking pan with parchment paper, leaving overhang on two sides for easy lifting. Lightly grease the parchment.

Melt the Base: In a large microwave-safe bowl, combine white chocolate chips, sweetened condensed milk, and butter. Microwave in 20–30 second bursts, stirring well after each, until smooth and fully melted. This usually takes 1½–2 minutes total. Alternatively, melt gently on the stovetop over low heat, stirring constantly.

Flavor It: Stir in the cotton candy flavoring (or the raspberry and vanilla) and a pinch of salt. Mix until fully incorporated.

Divide and Tint: Split the mixture into two bowls. Tint one bowl with a tiny bit of pink gel food coloring and the other with blue. Start with a toothpick’s worth of gel and add more if needed. You want soft pastel shades.

Swirl the Colors: Spoon large dollops of pink and blue fudge into the prepared pan, alternating colors. Use a butter knife or skewer to gently swirl the colors together. Don’t overmix or you’ll lose the marble effect.

Add Toppings (Optional): Sprinkle mini marshmallows or pastel sprinkles on top and gently press them in. Avoid adding actual cotton candy now—it melts on contact with moisture.

Set the Fudge: Refrigerate for 2–3 hours, or until firm. For cleaner cuts, chill a bit longer.

Slice and Serve: Lift the fudge out using the parchment overhang. Warm a sharp knife under hot water, wipe dry, and cut into 1-inch squares. Serve slightly chilled or at cool room temperature.