McDonald's Shamrock Shakes or green shakes.

2 cups vanilla ice cream
1 cup milk
1/4 cup half and half
1/4 teaspoon MINT extract (not peppermint)
8 drops green food coloring
Makes 2 − 12 oz. shakes.
Mix all ingredients on high speed until smooth.
Stop blender, stir and blend again, if necessary to combine ingredients.