This recipe makes white-and-green-swirled cookies. To make the chocolate version, simply add 3 tablespoons unsweetened cocoa to the white half of the dough.
In a mixing bowl beat together the butter and sugar until fluffy; beat in the whole egg and salt. Stir in milk and extracts. Add flour a little at a time, beating until incorporated.
Divide dough in half. Add food coloring to one half of the dough and mix to achieve desired green color. Wrap white and green dough separately in plastic wrap, pat into a rectangle and chill until cold, at least 1 hour.
On a sheet of floured parchment, roll out white dough to just under ¼-inch thickness. Repeat with green dough on another sheet of floured parchment. Chill again until roll dough is cold, about 20 minutes.
Brush white dough with beaten egg white and place green dough on top, removing parchment. Using bottom sheet of parchment to help lift dough, roll into a log starting at one wide end. Seal the seam by brushing with egg white and pinching closed. roll log tightly in parchment and chill about 1 hour.
Heat oven to 350ºF. Slice log into ¼-inch-thick rounds. Place on parchment-lined baking sheets and bake 16 to 18 minutes until done but not browned. Let cool and enjoy!
Notes
• I make one batch of white and green cookies and a separate batch of chocolate and green cookies. To make the chocolate version, simply add 3 tablespoons unsweetened cocoa to the white half of the dough.