01 -
Preheat oven to 350°F. Line small baking sheet with parchment paper or silicone mat.
02 -
Combine melted butter, sugar, egg yolk, vanilla extract and red food coloring until well mixed.
03 -
Sprinkle flour, cocoa powder, baking soda and salt over dough. Stir just until combined.
04 -
Divide dough into 6 portions, roll into balls, then roll in extra sugar. Space on baking sheet.
05 -
Bake 10-12 minutes until spread and crackled. Let rest 2 minutes on sheet, then move to cooling rack.
06 -
After 10 minutes cooling, press chocolate heart into center of each cookie. Refrigerate 30 minutes to set.