Reduced cider dressing

Gourmet (the late lamented Gourmet) published a recipe for a salad dressing with reduced apple cider in it, and I keep having to look it up, and it's not an easy search, because of cider vinegar, and because the dressing's not in the title; it's like Fennel & Oak Leaf Lettuce Salad - so I decided to make a copy of my version, here, where it'll be easier to retrieve:

• 3/4 cup apple cider
• 3 tablespoons cider vinegar, or other - I used a cherry Balsamic from Vom Fass that was lurking in the cupboard
• 1 shallot, finely chopped - about one heaping TBLS
• 1 teaspoon grainy mustard - like Boetje's
• salt and freshly-ground black pepper to taste
• maybe a pinch of sugar, if you use cider vinegar
• 1/3 cup olive oil

Boil apple cider in a small saucepan or skillet over moderate heat until it's reduced to about 2 tablespoons, and is syrup-y. Cool. Meanwhile, add the chopped shallots to the vinegar in a bowl, than add the mustard, salt, and pepper and whisk in the cider syrup. Drizzle the oil, whisking to combine. Enough dressing for about 10 cups of greens.