Plenty of chestnuts will be available for roasting on an open fire this season, but supply chain slowdowns are expected to affect the cost and availability of many other holiday treats across the country during the holidays. Making “George Washington’s Eggnog,” a popular online recipe, could be a pricey treat this year. The recipe calls for one quart of cream or milk, which is up around 40 cents per gallon from the average last year, as dairy farmers struggle to find a way to get their products to market. Then there’s the one dozen tablespoons of sugar, which will cost about 3 percent more than last year. The recipe also calls for a one pint of brandy, a half-pint of rye whisky and Jamaica run, and one-quarter pint of sherry. Alcoholic beverages will cost consumers around 2 percent more this year compared to 2020, according to the U.S. Bureau of …