Step 1

Soften butter to room temperature.

Step 2

Place butter, dark brown sugar, powdered sugar, cinnamon, and nutmeg in a bowl.

Step 3

Use a mixer to combine until smooth.

Step 4

Place a heaping tablespoon and a half of the mixture in a mug.

Step 5

Add 1½ ounces (1 jigger) of rum.

Step 6

Fill the mug with boiling water and stir to combine.