Cut pork into 1" cubes and brown in hot vegetable oil. Add garlic, onions and mushrooms and sauté 2 minutes. Add pineapple and celery and sauté 2 minutes. Put in a casserole dish.
Mix brown sugar, vinegar, ginger and water in a medium saucepan. Bring to a boil.
Shake cornstarch with a little water in a covered container to make a very thin paste. Add the cornstarch mixture to the sugar and
vinegar mixture and bring back to a boil to thicken. Pour over pork and vegetable mixture and bake at 350 degrees for 25 minutes.
Can be prepared ahead of serving and reheated