Step 1

Combine heavy cream, malted milk powder, brown sugar, and salt in a mixing bowl or bowl of a stand mixer. Beat, using the whisk attachment, electric beaters, or a whisk, until dry ingredients are evenly incorporated and cream forms soft peaks.

Step 2

Combine hot coffee, spiced rum, and simple syrup in a prewarmed mug. (You can prewarm it by pouring hot water into it, letting it stand for 1 minute, then draining.) Using a spoon, dollop whipped cream on top of coffee and top with freshly grated nutmeg, if using. Serve right away. (Note that you may have more whipped cream than the mug can accommodate; feel free to add more as you drink, or use some for the next round.)