In a large mixing bowl, combine the unsalted butter and shortening. Beat them together until the mixture is smooth and creamy—about 2-3 minutes should do the trick.

Next, introduce the mint extract to the bowl and mix until well combined.

Gradually, add the powdered sugar, ½ cup at a time, mixing well after each addition—approximately 5 minutes will ensure everything blends beautifully.

Now, pour in the milk one tablespoon at a time to get the right spreadable consistency.

Finally, incorporate the green gel coloring until your frosting reaches a lovely light green shade.