1. In a 6-quart pressure cooker over high heat, frequently stir lamb until browned, about 15 minutes. With a slotted spoon, transfer lamb to a bowl.
2. Meanwhile, rinse common mushrooms, trim stem ends, and quarter mushrooms. Rinse shiitakes, discard stems, and slice caps.
3. In cooker, stir common mushrooms, shiitakes, onions, carrots, garlic, and pancetta until onions are lightly browned, about 10 minutes. Add lamb and juices, wine, basil, rosemary, and cloves.
4. Seal cooker. Following manufacturer's instructions, bring to maximum pressure (15 lb.); adjust heat to stabilize cooking rate. Cook 20 minutes. Release pressure quickly, running cold water over pan.
5. Open pan. If desired, discard cloves. Add peas to pan. Mix cornstarch with 2 tablespoons water and stir into mixture, then stir stew over high heat until boiling. Season to taste with salt and pepper.
6. Serve with mashed potatoes or cooked rice.