The first step is to line a 9×9 square baking pan with parchment paper and spray it with cooking spray. Make sure the edges of the parchment paper extend above the pan so you can easily remove the fudge from the pan after it sets. 

In a medium heat-safe bowl, place the chocolate chips and food coloring. Set aside. 

In a large microwave-safe bowl (preferably glass as it gets quite hot!), melt the butter with a paper towel or paper plate placed on top of the bowl to prevent splatters – in 30 second intervals, about 1 ½ minutes, or until it is melted.

Add the sugar and half and half. Mix well, and then microwave for 3 minutes. Stir again, and microwave for an additional 2 minutes. Stir and microwave for 3 more minutes, and then a final stir and 2 ½ minutes.

If at any point the butter separates, just continue stirring, it will reconstitute itself. Also, scrape down the sides of the bowl as needed throughout this whole step. After the final time, the mixture bubbled furiously after being mixed. 

Add room temperature marshmallow creme fluff, and stir until well combined. This takes a bit, but continue to stir until the fluff is fully absorbed.

Add white chocolate chips and vanilla. Continue to stir until the chocolate chips are fully melted and smooth. 

Split the mixture in half into a third bowl, and add one-half of the melted chocolate to the medium bowl with the chocolate chips and food coloring from step 2 and mix until the chocolate chips are melted and smooth.

Scoop the two mixtures by the spoonful into a random pattern at the bottom of a prepared pan.

Remove any large air pockets by dropping the pan on the work surface a couple of times. You only need to drop it about 1” from the work surface.

Then, take the sharp side of a butter knife, spray with a bit of cooking spray, and run it around randomly in the pan to create a swirled effect in the fudge.

Don’t move it around too much or it will muddle the colors together.

Allow the fudge to cool completely (at least 2 hours) before lifting the parchment paper out of the pan and cutting.