Rim the Glass: Lightly wet the rim of a shot glass with water or simple syrup, then dip into cinnamon sugar to coat.
Chill the Ingredients: Fill a cocktail shaker with ice cubes.
Shake the Liquids: Pour RumChata and Fireball into the shaker. Add a splash of heavy cream if you want a creamier consistency. Shake vigorously for 10–15 seconds until frothy and well chilled.
Strain and Serve: Strain the mixture into the prepared shot glass.
Optional Garnish: Sprinkle a tiny pinch of cinnamon sugar on top just before serving.