Preheat oven to 350 degrees Fahrenheit. Beat butter with sugar until light and fluffy. Add in peppermint extract and egg yolks. Add green food color slowly until you reach a minty green. (Color will fade slightly during baking.)

Beat in flour, baking powder and salt. Shape dough into one-inch balls, and place one inch apart on lined cookie sheets. Using your index finger poke a hole in the center of each cookie, not completely through to the bottom.

Bake for 12 minutes, rotating midway. As soon as you remove them from the oven, reshape your indentation. DO NOT use your finger this time! The back of a wooden spoon works well.

While cookies are baking, place the chocolate chips, whipping cream, and butter in a microwave safe bowl and microwave for one minute. Mix until smooth. When the cookies are cool, fill the indentations with a teaspoon of chocolate. When the chocolate is nearly firm garnish with mint chocolate.