Lightly grease a large baking sheet and set aside. Grease a spatula and your hands to prevent sticking.

In a large microwave-safe bowl, combine the mini marshmallows and 3 tbsp of butter. Heat on high for 1 minute. Stir until smooth. If not fully melted, heat in additional 30-second intervals, stirring each time.

Immediately stir in about two-thirds of the gelatin powder, the vanilla extract (if using), and the pinch of salt into the melted marshmallow mixture until well combined.

Quickly add the Rice Krispies cereal to the bowl. Use the greased spatula to fold and stir until all cereal is evenly coated with the marshmallow mixture.

Allow the mixture to cool slightly until manageable. Scoop a handful and form into a 5-6 inch log shape. Place on the prepared baking sheet.

Use the handle of a wooden spoon to press a winding line down the center of each log. Then, use a knife tip or toothpick to create squiggly lines and wrinkles all over the surface to resemble a brain.

In a small bowl, mix the remaining one-third of gelatin powder with the cocoa powder and powdered sugar. Use a fine-mesh sieve to lightly dust this mixture over the brains, focusing on the crevices.

Let the brains set and cool completely, about 30 minutes.

For the glaze, combine jam and 1 tbsp of water in a small microwave-safe bowl. Heat for 30-45 seconds until runny. Stir. Add more liquid if too thick.

Drizzle the warm blood glaze over the cooled brains. Serve immediately and enjoy the spooky festivities!