It’s 28 degrees outside, but feels like 12. The city is digging out from the winter’s first snowstorm. And you’ve been led to a table next to a crackling fire at Post 390 in Copley Square. So far, so good. This is the right time and place to experience the Fat Monk, the Back Bay restaurant’s inventive take on a traditional hot buttered rum.

“We roasted sugar pumpkins dusted with warm spices — cinnamon, nutmeg, etc. — and let them rest in the rum with a split vanilla bean for a few days,’’ says beverage manager Jason Percival in an e-mail. “After that, it was drained off, and browned butter was whisked into it. We then put it in the refrigerator for two days, after which we strained it through a cheesecloth.’’

Sherry brings sweetness and acid to the mix, he says, and orange peel steeps in hot water, lending an uplifting flavor. This warm drink may dance smoothly across the palate, but don’t be fooled. It’s a complex potion. JAMES REED

Fat Monk: makes 1 cocktail

1½ ounces Old Monk rum (infused with roast sugar pumpkin, cinnamon, nutmeg, and split vanilla bean)

½ ounce Pedro Ximenez sherry (or any other sweet sherry)

1 pat butter

4 ounces hot water poured over fresh orange peel

¼ slice orange

1. In a mug, stir the rum and sherry until well blended.

2. In a small saucepan over medium heat, heat the butter until light brown. Whisk into the rum and sherry mixture. Strain through a cheesecloth and transfer back to mug.

3. Pour the hot, orange-scented water (the same temperature you’d use for tea) into the mug.

4. Stir and transfer to a brandy snifter.

5. Garnish with the ¼ slice of orange. Adapted from Post 390

James Reed can be reached at jreedwrites@gmail.com. Follow him on Twitter @jreedwrites.