Preheat oven to 350 degrees.
In a large bowl or stand mixer, beat together egg, butter, and sugar until very well combined. Add flour and vanilla, mix until a thick dough forms. Separate dough into 3 small rounds and tint with food coloring, kneading until the color is well mixed.
Roll dough between two pieces of parchment paper until 1/4” thick. Cut into hearts with Sweet Creations heart cookie cutters. Transfer cut cookies to a parchment-lined baking sheet. Bake in preheated oven for 8-11 minutes, or just until edges begin to brown.
Assemble into sandwich cookies with Our Favorite Buttercream Frosting, roll edges into nonpariels sprinkles.