Step 1

Preheat the oven to 350, and line a small baking sheet with parchment paper (or use a silicone mat).

Step 2

Stir together the melted butter, sugar, egg yolk, vanilla extract and red food coloring. Stir very well to combine.

Step 3

Next, sprinkle the flour, cocoa powder, baking soda and salt evenly over the dough, and stir just to combine.

Step 4

Press the dough flat and evenly in the bowl, and then divide it in half by eye. You should get 3 cookies from each half.

Step 5

Roll each dough ball in your hands, roll lightly extra granulated sugar, and then space evenly on the prepared baking sheet.

Step 6

Bake for 10-12 minutes, until they spread, start to crackle and appear dry on top.

Step 7

Let the cookies rest on the baking sheet for 2 minutes before moving them to a wire rack to cool completely.

Step 8

After the cookies have cooled for 10 minutes, press a white chocolate heart into the center of each cookie. Move the cookies to the fridge (so the hearts don't melt too much) to set for 30 minutes.

Step 9

Bring to room temperature before serving.