Rim a chilled martini glass with a thin layer of frosting, then dip and twist it in sprinkles until evenly coated.
Freeze the rimmed glass for 2 to 3 minutes to set the frosting.
Fill a cocktail shaker two-thirds full with ice.
Add the vodka, RumChata, amaretto, half-and-half, and simple syrup if using.
Shake hard for 15 to 20 seconds until frothy and well chilled.
Strain into the prepared glass and serve immediately.
Notes
Swap heavy cream for half-and-half and skip the simple syrup for a lighter, less sweet version. Use RumChata for a sweeter, more spiced flavor, or Irish cream for a boozier one.
Keyword holiday cocktail, sugar cookie martini, sugar cookie martini recipe