Feeling cold? Cuddling up with a cup of hot cocoa loaded with marshmallows would definitely warm your night. But lo! When you reach into the bag, you find that all the white puffs seem to have morphed into one. Relax. To separate them, add a teaspoon of cornstarch to the bag and shake. The powder sops up the condensation that forms inside the plastic bag and causes stickiness while the friction of the starchy molecules helps force the puffs apart. Keep your leftover marshmallows in an airtight container to avoid future clumping.