The sour is the most forgiving formula in the cocktail canon: spirit, citrus, sweetener, balanced. In October the best version swaps the usual whiskey for Calvados, the apple brandy of Normandy, and the simple syrup for a spiced reduction of fresh cider. The result tastes like an orchard in a coupe, bright rather than heavy, and it is easy enough to make for a crowd.

Why Calvados

Calvados is distilled from cider made from Normandy apples (and, in some cases, pears), then aged in oak. It is a protected appellation with three designations:

• Calvados AOC, the broadest category, usually column-distilled.
• Calvados Pays d’Auge, double-distilled in copper pot stills, the style with the most depth.
• Calvados Domfrontais, made with at least 30% perry pears, lighter and more floral.

Age statements matter. VS or Fine means at least two years in oak; VSOP or Vieille Réserve at least four; XO at least six. For a cocktail, a VSOP from the Pays d’Auge is the sweet spot: enough wood and fruit to stand up to lemon, without wasting an XO you would rather sip. Christian Drouin, Roger Groult and Boulard are reliable names to look for.

The spiced cider syrup

This is what makes the drink. Reducing fresh cider concentrates its apple flavor far beyond anything a bottled syrup can deliver.

• 2 cups fresh, unfiltered apple cider
• 1 cinnamon stick
• 3 whole cloves
• 2 wide strips of orange peel
• 1/4 cup demerara sugar

Simmer the cider with the cinnamon, cloves and orange peel until reduced by half, about 15 to 20 minutes. Off the heat, stir in the sugar until dissolved, strain and cool. It keeps for two weeks in the refrigerator.

The cocktail

• 2 oz Calvados (Pays d’Auge VSOP)
• 3/4 oz fresh lemon juice
• 3/4 oz spiced cider syrup
• 1 egg white (optional, for a silky foam)
• 2 dashes Angostura bitters
• A thin apple slice, to garnish

1. Add the Calvados, lemon juice, syrup and egg white, if using, to a shaker. Shake without ice for 15 seconds.
2. Add ice and shake hard for another 10 to 12 seconds.
3. Double-strain into a chilled coupe.
4. Dot the bitters on the foam and float a thin slice of apple on top.

Skip the egg white and serve it on a large cube in a rocks glass for a sharper, more rustic drink.

Batching for a dinner party

Multiply the Calvados, lemon and syrup by eight and combine in a pitcher up to two hours ahead, without the egg white. Keep it cold and shake each drink to order, or stir the pitcher over ice and pour. Squeeze the lemon the same day; pre-bottled juice flattens the drink.

What to serve with it

The Calvados Cider Sour wants salt and fat: aged cheddar, a wedge of Camembert from the same corner of Normandy, or spiced nuts. It is also the right opening for a long fall dinner. Follow it with red wine braised short ribs and finish with a tarte tatin, with a small pour of the same Calvados alongside.

For more seasonal ideas, start with the Fall Edit and browse the rest of At the Table.