In a microwave-safe bowl, combine 3 tablespoons of unsalted butter and 6 cups of pink and white marshmallows. Microwave in 1-minute intervals until melted and smooth, about 3 minutes.

Add 8 cups of Rice Krispies cereal and a few drops of red food coloring. Stir until all the cereal is evenly coated.

Line a baking tray with parchment paper. Lightly oil your hands and spoons, scoop out mounds of the mixture, and shape them into brain-like forms.

Using a lightly oiled knife, create a line down the center of each brain shape to divide them.

Drizzle or dot red icing across the top of each brain and let them set at room temperature for 4-5 hours.