1. Prepare ingredients
Preheat oven to 450. Wash and dry produce. Trim and halve brussels sprouts lengthwise. Strip thyme leaves from stems: chop leaves until you have 2 teaspoons. Trim, peel, and cut carrots on a diagonal into ½-inch-thick pieces. Halve, peel, and finely chop onion.
2. Roast Veggies
Toss brussels sprouts on one side of a baking sheet with a drizzle of oil, half the chopped thyme, and a pinch of salt and pepper. Toss carrots on empty side with a drizzle of oil, salt, and pepper. Roast on top rack, tossing halfway through, until tender and crisped, about 20-25 minutes.
3. Sear Pork
While veggies rest, pat pork dry with paper towels; season all over with salt and pepper. Heat a drizzle of olive oil in a large pan over medium heat. Add pork and sear turning occasionally, until browned all over, 4-8 minutes. (it’ll finish cooking in the next step). Transfer to a second baking sheet.
4. Roast Pork
Roast pork on middle rack until cooked through, 10-12 minutes. Transfer to a cutting board and let rest a few minutes, then thinly slice crosswise.
5. Make Pan Sauce
Heat a drizzle of olive oil in pan used for pork over medium heat. Add onion and remaining chopped thyme. Cook, stirring, until softened, 1-2 minutes. Stir in stock concentrate, vinegar, jam, an d1/4 cup water. Simmer until thick and saucy, 2-3 minutes. Remove pan from heat and stir in 1 tablespoon butter until melted. Season with salt and pepper.
6. Serve
Divide brussels sprouts, carrots, and pork between plates. Drizzle pan sauce over pork and serve.