Prep the glass: Pour a small line of honey or simple syrup onto a plate.
Dip the rim of a rocks or coupe glass in the syrup, then dip it into the cinnamon-sugar mixture. Set the glass aside.
Build the cocktail: In a cocktail shaker, add whiskey, RumChata (or cream liqueur), vanilla simple syrup, milk or half-and-half, and cinnamon.
Add ice: Fill the shaker with ice about three-quarters full. Cold helps soften the spice and creates a silky texture.
Shake well: Shake for 12–15 seconds until the shaker feels frosty.
This chills and lightly aerates the drink for a creamy finish.
Strain and serve: Strain into your prepared glass over fresh ice (for a rocks glass) or without ice (for a coupe).
Garnish: Add a cinnamon stick or a small dusting of cinnamon on top. Serve immediately.