Position a rack in the center of the oven and heat the oven to 425°F. In a 12-inch oven-safe skillet, cook the pancetta over medium-low heat until brown, turning as necessary, 5 to 8 minutes. Transfer the pancetta to a plate lined with paper towels (it will crisp as it cools);remove the skillet from the heat and cool slightly.
Put the skillet over medium heat and add 1-1/2 Tbs. of the butter and the olive oil. When the butter has melted, arrange the leek and carrot pieces on the bottom of the pan in a snug single layer. Season with 1/2 tsp. salt and cook, undisturbed, until the bottoms of the vegetables are browned (the leeks may be slightly darker than the carrots), about 5 minutes. Using tongs, flip the vegetables and add 1/3 cup of the wine. Continue to cook undisturbed until the wine has almost evaporated, 2 to 3 minutes. Add the chicken broth, half of the thyme, and the coriander, and transfer the skillet to the oven.
Roast until the carrots are tender when pierced with a fork, about 30 minutes.
Transfer the vegetables to a warm platter. Put the skillet over medium-high heat (use caution; the handle is hot), add the remaining 2 Tbs. wine and stir for a few seconds, scraping up any browned bits. Remove the skillet from the heat, add the remaining 1 Tbs. butter and 1/2 tsp. thyme, and stir to melt the butter. Pour the sauce over the vegetables, crumble the pancetta over top, and serve.
Serve with a roasted leg of lamb for a special occasion or with a simple roasted pork loin for a Sunday meal.