Using a food processor, finely chop the peanuts. In a large skillet, heat the oil, 2 turns of the pan, over high heat. Add the pork and cook until browned, about 5 minutes; season with pepper. Add the mushrooms, scallions, garlic and ginger; toss for 2 minutes. Push the ingredients to the side of the pan and add the peanut butter to the center to melt. Whisk in the apple juice, tamari and hot sauce. Stir in the peanuts.
Spoon the satay into a serving bowl or individual bowls. Serve the lettuce wedges alongside. Scoop the satay mixture into lettuce leaves to wrap up as you eat.