Rub the lemon wedge along the rim of the glasses. Place the sanding sugar on a small plate and dip the rim of glass into sanding sugar. Set aside.
Put the ice cream, ½ cup of Bailey's, milk, and peppermint in a blender and blend.
Add the green food coloring to get the preferred shade of green.
Pour into glasses.
In a cold metal bowl, whip the cream, 1 teaspoon of Bailey's Irish Cream and icing sugar together until peaks form.
Add whipped cream to glasses, top with Lucky Charms marshmallows and a pinch of sanding sugar.
Notes
Chill the glasses: Cold glasses keep the shake thick longer. Blend well: Smooth blending gives the shake a perfect texture. Taste and adjust: Add more peppermint or Irish cream to taste. Serve right away: The shake is best when fresh and cold.