Preheat oven to 350 degrees F and prepare a metal baking sheet lined with parchment paper.
With an electric mixer or stand mixer fitted with a paddle attachment, cream butter, sugar, and salt in a large mixing bowl.
Add flour and matcha and mix until dough forms.
Add 3 tbsp milk and mix. At this point the dough should be thin enough to pipe, but if not, add up to one tablespoon more of milk.
Transfer cookie dough to a piping bag fitted with a star tip.
Pipe circles of matcha dough onto a lined baking tray in a wreath shape, about two inches in diameter and one inch apart, as cookies don't spread much during baking. Top with sprinkles, if using.
Bake cookies for 12 minutes or until cookies easily lift off the tray. If working in a very warm kitchen or if you feel the cookie dough became too thin and warm as you were working with it, you can chill the dough before baking.
Leftovers keep in an airtight container at room temperature.