Melt the butter and marshmallows. Bring a pot of water to a gentle simmer and position a heat-safe bowl over the top, making certain that the bottom of the bowl does not come into contact with the water.

Place the softened unsalted butter and marshmallows in the bowl. Stir continuously for 2–4 minutes, or until both ingredients have melted together into a completely smooth mixture. Using gentle indirect heat helps the marshmallow base melt evenly without scorching or developing lumps.

Add the salt and red coloring. Remove the bowl from the heat. Immediately mix in the salt along with enough red food coloring to achieve the desired shade.

Stir vigorously for approximately 30 seconds so the coloring is distributed evenly throughout the melted marshmallow mixture.

Coat the puffed rice cereal. Add the puffed rice cereal to the tinted marshmallow mixture. Fold gently yet thoroughly until each piece of cereal is evenly coated.

Continue working while the mixture remains warm and flexible, as it will become more difficult to shape as it cools.

Form the brain shapes. Lightly coat your hands with cooking oil or butter to prevent sticking. Scoop out portions of the cereal mixture and mold each one into an oval approximately the size of a tennis ball.

Press your thumb lengthwise into the center of each oval to form the distinctive central brain groove. For a deeper indentation, a chopstick or the handle of a wooden spoon may be used instead.

Create the vein details. Allow the shaped treats to firm slightly for 5–10 minutes.

Dip a toothpick into red food coloring and draw vein-like markings over the surface of each brain. Begin near the central ridge and extend irregular branching lines outward to create a natural-looking, asymmetrical pattern.