In large dish pour wine over brisket and scatter garlic slices. Marinate in refrigerator for 24 hours, turning after 12 hours.
Remove beef and pat dry. Resume marinade.
Combine mustard and soy sauce and spread over meat. In Dutch oven or large heat proof casserole heat half of the oil; brown brisket all over. Season meat with salt and pepper. Remove from pan and set aside.
Add remaining oil to pan. Sauté onions, carrots and celery until softened. Sprinkle flour over vegetables and cook for 3 minutes stirring constantly. Add marinade, beef stock and tomato paste. Bring to a boil and stir until blended. Taste and adjust seasoning. Return brisket to pot.
Bake covered in 325º oven for 21/2 hours or until meat is tender.