I started making hot buttered rum the first winter I went keto, and I've been tweaking it every year since. The original version I grew up with was loaded with brown sugar and honey, so I had to figure out how to get that same warm, maple-adjacent sweetness without the carbs. Golden monk fruit was the answer. Not the white powdered kind, which is too clean and neutral, but the golden version that has this caramel warmth to it. That one detail is what makes the whole drink work.
The base is simple. Hot water, a shot or two of dark rum, golden monk fruit (or ChocZero maple syrup if you want it even more syrupy), and a tablespoon of butter floating on top. That butter is the whole point. It melts slowly into the drink, and by the time you stir it in with the cinnamon stick, you've got this silky, rich layer that coats every sip. I've had readers ask if the butter just sits there or melts in. The answer is both. It floats first, then you stir it down.
One thing I never skip is the nutmeg. It doesn't read as nutmeg on its own. It just makes the whole thing taste warmer. I've made it side by side, with and without, and the version with nutmeg wins every time. Just a pinch.
If you want a creamier version, throw everything except the cinnamon stick into a blender or milk frother for about 10 seconds. I started doing this two winters ago and I haven't gone back. The butter emulsifies into the liquid and you get this almost latte-like foam on top. Completely different drink. If you like my white hot mocha or pumpkin spice latte, you'll love what the frother does here.
A quick note on rum. Not all spiced rums are low carb. Some brands add sugar during the flavoring process, and it doesn't always show up on the label. I stick with plain dark rum (Bacardi Black or Gosling's) because the carb count is zero and predictable. If you prefer bourbon or brandy, those work just as well. I've made this with Maker's Mark and it's fantastic.
This is my go-to when I want something that feels like a real winter keto cocktail, not a diet drink. I make it after skiing, after shoveling the driveway, after putting the kids to bed on a cold night. If you're looking for warm weather options, my mojito and appletini are where I'd start. And if you want another cozy one, my frozen hot chocolate is surprisingly good even in winter. But when the temperature drops below freezing, this is what I'm pouring.