Preheat oven to 425 degrees. Line a baking sheet with parchment paper.
In a small mixing bowl, combine ground flaxseed and water. Whisk well and set aside for 5 minutes. This will serve as your “egg” in the recipe.
In a large mixing bowl, combine shortening and sugar; beat until light and fluffy. Add flaxseed mixture and vanilla; continue to beat until well combined. Gradually mix in flour, cocoa, baking soda, and salt.
Roll out dough on a floured surface to ¼ inch thick. Using a heart cookie cutter, or shape of choice, cut out cookies. Roll out scraps and repeat until all dough has been used.
Transfer hearts to baking sheets. Bake for 10 minutes. Remove from oven; let cool on baking sheet for 2 minutes, then transfer to a wire rack to cool completely before decorating. Decorate however your Valentine heart desires! I frosted mine in melted chocolate and finished off with fun sprinkles and a simple powdered sugar glaze.