I’m cheating here, because this isn’t entirely cooked in the oven, but the brief roasting is what helps Brussels sprouts achieve their optimum potential, instead of waterlogging them in a saucepan. I ate a similar dish at Rotisserie Georgette in New York—a restaurant that specializes in roast chicken—then came straight home and made this. It’s been a regular in my house ever since, and not just at Christmas.
Lay the sprouts in a single layer in 1 or 2 roasting pans. Add 2 tablespoons of olive oil, season, and toss.
Roast for 20 minutes, or until the edges begin to look brown and frazzled (they can turn from frazzled to burned very quickly, so keep an eye on them). They won’t cook right through, but will finish cooking later.
Heat the remaining 1 teaspoon oil in a sauté pan and fry the bacon lardons until golden and cooked through. Lift out with a slotted spoon.
Remove all but 1 tablespoon of fat from the pan (fat will have rendered from the bacon). Core the apple and cut it into fine crescents, then add to the pan with the onion. Cook over medium heat until golden and soft (though the apple shouldn’t be collapsing). It will take about 5 minutes.
Add the sugar, both vinegars, the wine, and the mustard. Return the bacon and season to taste. Toss well and cook until the wine has reduced by about half, then add the sprouts and cook until they are only just tender, but not floppy (all the juices around them should have reduced).
Toss in the butter, if you’re using it. Check the seasoning and serve.