I chose to use Fruity Pebbles to fill my cascarones because we will be smashing them outside at the park, and I didn't want to leave pieces of confetti outside. You could also use birdseed, glitter, or small toys.
Next, close the hole in the eggshell by outlining the rim with glue and covering the opening with a small square of tissue paper (any color).
This step is optional: after the glue and tissue paper dry, add more glue on top of the tissue around the top 1/3 of the egg. Spread the glue into an even coating with a small paintbrush. Roll the egg in a plate of glitter for a sparkly covering to hide the tissue paper. Glitter is fun to use, but any type of confetti could also be used to cover the tissue paper.
Now you're ready to head to the park and break your cascarones on top of friends' heads, bringing them good luck (and a lot of laughs!). Enjoy!