Cream the butter and sugar together until smooth, and then beat in the Jell-O.
Beat the eggs in until the mixture is smooth, and then finish out by beating in the dry ingredients.
When everything is well-incorporated, scoop the dough by the tablespoon onto a prepared cookie sheet, spacing them about two inches apart.
Bake for 8 minutes or until the edges just start to brown.
Let the cookies cool completely before frosting them.
For the frosting, combine the Jell-O, sugar, vanilla and egg white in a mixing bowl and beat together until they're well combined.
Add in the boiling water and beat the mixture for about 7 minutes to get the frosting nice and fluffy. To make it easier to spread on the cookies, refrigerate it for about 30 minutes to let it set up a bit.
Spread or pipe the frosting onto the finished cookies and store them in an airtight container. (Fair warning: this frosting is more like a whipped cream, so it won't harden, and you won't be able to stack the finished cookies.)