Beat butter until smooth. Add milk and powdered sugar. Begin with 4 C of powdered sugar and add more as needed to reach desired consistency. (Should be fairly thick but not so thick that you won’t be able to squeeze it out of a piping bag to frost.) Add coconut extract and mix in thoroughly.
Spoon frosting into a Ziploc bag, snip off one corner and pipe into center of cookie. Spread a little with a knife.