Pumpkin Stuffed with Vegetable Stew

Name: Pumpkin Stuffed with Vegetable Stew
Ingredients: 1 fennel bulb with fronds; 2 medium parsnips (1/2 pound total), peeled, quartered, cored, and cut into 1-inch pieces; 1/2 pound celery root (sometimes called celeriac; 1/2 of 1 medium), peeled and cut into 1-inch pieces; 3 medium carrots, peeled and cut into 1-inch pieces; 14 small shallots (about 1 pound), peeled and left whole, plus 1/2 cup chopped; 3 tablespoons olive oil, divided 2 red bell peppers; 1 (8- to 9-lb) pumpkin (preferably cheese, pie, or Sweet Meat variety); Roasted-vegetable and wine sauce , heated; 3 tablespoons unsalted butter; 1/2 pound fresh cremini mushrooms, trimmed and halved; 1/4 pound fresh chanterelle mushrooms, trimmed; 1 pound seitan (seasoned wheat gluten), cut into 1/2-inch pieces; 1 teaspoon chopped thyme, divided; 1 tablespoon chopped flat-leaf parsley; 1/2 teaspoon grated lemon zest