Heat the oven to 350 degrees. Toss the brussels sprouts with 2 tablespoons of the olive oil. Roast them on a rimmed baking sheet for about 45 minutes, until fork tender.

Meanwhile, heat a medium sauté pan and cook the pancetta over medium-high heat for 3 to 4 minutes, until the fat is rendered and the pancetta is crispy. Remove with a slotted spoon and place it on a plate lined with a paper towel.

In another sauté pan, heat the remaining 2 tablespoons of olive oil over medium heat until just shimmering. Add the shallots and garlic and cook until the shallots are translucent. Add the mushrooms and cook for 2 to 3 more minutes, until the mushrooms are cooked through. Add the stock and simmer for 1 to 2 minutes, until most of the stock is absorbed.

When the brussels sprouts are roasted, place them in a large bowl. Add the pancetta and the wild mushroom mixture and toss gently. Season with salt and pepper.