Line your 9x9 inch baking dish with parchment paper, allowing some overhang for easy removal later.
In a double boiler or a microwave-safe bowl, combine the white chocolate chips, semi-sweet chocolate chips, and sliced butter. Heat until fully melted and smooth.
Remove from heat and stir in the sweetened condensed milk until fully incorporated.
Fold in the mini marshmallows, vanilla extract, and red food coloring. Mix gently to combine.
Carefully fold in the crushed Oreos, ensuring they are evenly dispersed.
Pour the fudge mixture into the prepared baking dish, smoothing it out with your spatula. Allow to set at room temperature for 2-3 hours or refrigerate for about 1 hour.
Once set, lift the fudge out using the parchment paper overhang, cut into squares, and enjoy!
