For the Cookie

1. Preheat oven to 300ºF. Prepare a baking sheet by lining it with parchment paper or a silicone baking mat.
2. Beat together the butter, brown sugar, egg yolk, and vanilla until light and fluffy. Mix in the flour, food coloring, and cocoa powder until soft dough forms.
3. Chill for at least 30 minutes or overnight.
4. Scoop out the dough by heaping tablespoons and roll them in the sugar* before placing on the prepared baking sheet (about 2 inches apart). Use your thumb (or the back of a round teaspoon) to make a small indentation in the cookie dough.
5. Bake for 10 minutes.

For the Cream Cheese Filling

1. Using an electric mixer, beat together the cream cheese, egg yolk, sugar, salt, and vanilla until smooth.
2. After the first 10 minutes of baking, use the back of a round teaspoon (too hot to use your thumbs!) to deepen the indentation in the cookies. Spoon a teaspoon of the filling into each indentation. It works best when you put the cream filling into a pastry bag and pipe it onto each cookie.
3. Bake for an additional 12 minutes, until filling is set. Let it cool for 10 minutes.
4. Melt the dark chocolate as directed on the package. Put the chocolate in a pastry bag (or ziploc bag) and drizzle onto the cookies. Let it set.