For the milkshake: Put the ice cream, milk, and peppermint extract in a blender and blend for a few minutes until smooth. Add the food coloring until you reach the desired shade of green (about 8 drops). If you want your milkshakes a little thinner, add more milk. Divide between two glasses.
For the whipped cream:
In a cold large bowl, beat the cream until it starts to thicken. Slowly beat in the powdered sugar then beat in the vanilla or Irish cream. Whip until stiff peaks are formed (when you pull the beaters straight up, it should make little peaks that won’t fall over). Top the milkshake with the whipped cream and cherries.