Place the onions in the bottom of a 5 quart slow cooker. Layer carrots over the onions, followed by layers of celery, mushrooms, and pineapple. Season pork chops with salt and pepper. Place them on top of the vegetables. If you like, you may brown them in a hot skillet first.
In a medium bowl, stir together the pineapple juice, sherry, cider vinegar, and soy sauce. Stir in the cornstarch until dissolved. Mix in the brown sugar, white pepper, ginger, mustard powder, garlic, salt, pepper, hot pepper sauce and tomato paste. Pour this over the pork chops and vegetables. The sauce will taste less sharp after a few hours in the slow cooker. Cover, and cook on Low for 6 to 8 hours, or on High for 3 to 4 hours.
