Mix all ingredients together and stir until sugar mixture looks like wet sand. Use 1/4 teaspoon to fill up mold cavities and use the back of a spoon to pack the sugar into the mold. Scraping off any extra sugar mixture.
Cover the mold with a parchment lined cookie sheet and holding on to both, invert the whole thing over to un-mold the skulls. Tap the mold gently to release the wet sugar cubes. Let dry for 4 hours or overnight. Repeat with the rest of the sugar mixture.
Once dry, store in a sugar bowl or a plastic container and add them to coffee, tea, and oatmeal for a festive Halloween breakfast!