Arrange your rum, cream liqueur, butterscotch syrup, milk, butter, and vanilla on your workspace before you start mixing.

Pour the butterscotch syrup into your rocks glass or coffee mug as your base layer.

Using your jigger, measure 1.5 ounces of spiced rum and pour it directly over the butterscotch syrup.

Pour 1 ounce of cream liqueur into the glass.

Drop in 0.5 teaspoon of cold butter directly into the glass or dissolve it in a small amount of warm milk first.

Add 2 ounces of whole milk or heavy cream to the glass.

Add 2 dashes of pure vanilla extract and stir the entire mixture vigorously for 20 to 30 seconds until the butter fully dissolves and all ingredients blend together.

Crown your cocktail with a generous dollop of whipped cream.

Optional: Rim your glass with a tiny pinch of sea salt before pouring or after by pressing whipped cream into it for extra flavor.