Preheat the oven to 425°F.
Season the chicken with salt and pepper. In a large, ovenproof skillet, heat 2 tablespoons shortening over medium-high heat. Add the chicken and cook, stirring, until browned, about 5 minutes. Add the onion and garlic, and cook, stirring, until softened, about 5 minutes. Stir in 2 tablespoons flour and cook, stirring, for 2 minutes. Add the broth and bring to a boil, scraping up any browned bits. Stir in the peas and carrots, lemon peel and lemon juice.