Preheat oven to 400 degrees.
In a large bowl, or the stand of a kitchen mixer, beat butter until creamy and smooth. Add in sugar, vanilla and one package of the JELL-O and beat until light and fluffy. Add in baking soda and flour, beating at medium speed until you have a thick, crumbly dough.
Roll dough into one inch balls and slightly flatten with the bottom of a glass. Sprinkle the tops with the leftover JELL-O mix.
Bake for 6 minutes, or until edges begin to turn golden brown.
Remove to cooling racks, or a kitchen counter lined with parchment, to cool.
