Adapted from Susie Middleton
2 lb. small Brussels sprouts, trimmed and halved lengthwise
1/4 cup extra-virgin olive oil
1 tsp. kosher salt
1 Tbsp. plus 1 tsp. balsamic vinegar
2 Tbsp. pure maple syrup
2 Tbsp. fresh orange juice
1 tsp. finely grated orange zest or lemon zest
4 Tbsp. cold unsalted butter, cut into 16 pieces and kept chilled
1. Preheat the oven to 475˚F. Line two large heavy-duty rimmed sheet pans with parchment paper. In a mixing bowl, toss the Brussels sprouts with the 1/4 cup olive oil and 1 tsp. of the salt. Divide the sprouts between the two sheet pans and arrange them, cut-side down. Roast until brown and tender, 16 to 18 minutes. (The tops will be dark brown and crispy and the sprouts should feel tender when pierced with a paring knife.) Transfer the sprouts to a mixing bowl.
2. Combine the balsamic vinegar, maple syrup, orange juice, and orange zest in a small saucepan. Heat the mixture over medium heat just until it’s hot (you will see a bit of steam), but not simmering. Remove the pan from the heat and add the cold butter, several pieces at a time, whisking constantly until the mixture is smooth and creamy. (Don’t reheat the mixture or the butter will break and the sauce won’t be creamy.) Pour the sauce over the sprouts and stir thoroughly but gently until most of the sauce has been absorbed. Transfer the sprouts and any remaining sauce to a serving platter and serve right away.