1 teaspoon chocolate syrup, or to taste (optional)
1 fluid ounce peppermint schnapps
2 fluid ounces chocolate liqueur
2 fluid ounces half-and-half
Drizzle chocolate syrup around the inside edge of a martini glass; place glass in the freezer.
Fill a cocktail shaker with ice; pour peppermint schnapps, chocolate liqueur, and cream into shaker. Cover, shake, and strain martini into the prepared martini glass.