Celery and Potato Gratin

Name: Celery and Potato Gratin
Ingredients: 1/3 cup olive oil; 2 onions, thinly sliced; 4 cloves of garlic, thinly sliced; 4 medium size celery stalks, peeled and finely diced; 1 teaspoons celery salt; 1 cup dry white wine; 1 cup chicken or vegetable broth; 1 can (28 ounces) plum tomatoes, half of juices reserved and chopped; 2 pounds waxy potatoes, peeled and cut into 1/4 inch rounds; 2 pounds celery root, peeled, quartered and cut into pieces of same thickness as the potatoes (keep cut celery root in acidulated water); Salt and freshly ground black pepper