At Scoma’s Restaurant in San Francisco, this holiday season 's batch of eggnog began 11 months ago. The process typically starts in late January, just after the previous year's celebrations are over. Nearly a thousand egg yolks, gallons upon gallons of heavy cream and roughly $1,000 worth of vanilla beans are mixed with sugar and a mega-cocktail of sherry, brandy and aged rum.

The concoction is then stored at 34 degrees Fahrenheit (1 degree Celsius) and and gets stirred weekly for months. Is it worth the wait? Customer Phil Kenny seems to think so. “It’s a wonderful, specialty drink," Kenny said of Scoma's recipe, which has been honed in recent years to take advantage of the boozy beverage’ s aging process.

"This takes eggnog to a different level.” Kenny and his wife, Laurie, aren't the only ones enjoying it this year. “A drink that you would sort of associate with grandma and grandpa on the holidays has become like a cult favorite here," Gordon Drysdale, Scoma’s culinary director, said earlier this month.

"We did not ever anticipate people actually being mad at us because we didn’t have it.” Eggnog's roots date back to medieval England and a drink called “posset,” which included hot milk or cream, alcohol and spices. Recipes have evolved in the centuries since then, and non-dairy and alcohol-free options abound in recent years.

But some — like the formula for the famous eggnog daiquiri at Lafitte’s Blacksmith Shop in New Orleans — stay the same, a.