Preheat Oven To 375 Degrees. Dress Brisket With 2 Tablespoon Olive Oil, Salt, Pepper, Thyme, And Crushed Garlic. Blanch Scallions For About 10 Seconds. Place Onion, Celery, Parsley, Carrots, And Scallions In Baking Dish With Briskets And Cook For 2 1/2 Hours. Combine More Crushed Garlic, Salt, Pepper, Oregano, Rosemary, Olive Oil, And Wine Vinegar. Refrigerate. Later Warm To Room Temperature And Serve As Dressing.