Step 1

Preheat oven to 350°. Cream butter, cream cheese and sugar until light and fluffy, 5-7 minutes. Beat in egg yolk, vanilla, food coloring and, if desired, extract. In another bowl, whisk flour and cocoa; gradually beat into creamed mixture.

Step 2

Using a cookie press fitted with a disk of your choice, press dough 1 in. apart onto ungreased baking sheets. In a small bowl, mix egg white and water; brush over cookies. Decorate as desired with nonpareils or sprinkles. Bake until set, 10-12 minutes. Cool on pans 2 minutes. Remove from pans to wire racks to cool completely.