Put into bowl and grind into a powder. A mortar and pestle works fine for this. Discard any large pieces. Add food coloring if desired. Allow to dry approximately 3 days until hard.
Eggshell chalk is for sidewalks only.
Seal both bags securely, removing excess air. Add ice and salt to larger bag and place smaller bag inside. Ice cream will be soft and ready to eat in 5 to 10 minutes. Top this off with chocolate syrup made from scratch. Cook over medium heat, bring to a boil.