Preheat oven to 350 degrees and line two cookie sheets with parchment paper

Using a medium bowl, whisk the flour, cocoa powder, baking soda, and salt until combined

Using a standing mixer, beat the butter, brown sugar, sugar, eggs, vanilla, and red gel food coloring until combined and fluffy

Gradually beat in the dry ingredients until a dough forms

Pour the red sanding sugar into a small bowl

Using a tablespoon, scoop some dough into your hands and roll it into a ball

Roll the dough into the red sanding sugar

Place the dough ball onto the cookie sheets, about 12 cookies per sheet

Bake in the oven for 10-12 minutes or until set around the edges

Remove from the oven and allow to cool for 1 minute before placing a chocolate heart into the center of the cookies

Allow cooling completely before enjoying!