Using a paring knife and your finger, stuff brisket all over with garlic. (I think this means to make slits in the meat and stuff small pieces of garlic into those slits and I would rub all over with garlic, to taste).
Place brisket in a baking dish or casserole and bake until browned on top, remove from oven, turn brisket and return to oven until browned on both sides.
Reduce oven temperature to 350 degrees F.
Add enough beef stock to casserole to come up 1 inch on sides, cover with foil and bake one hour.
While brisket is cooking, heat a large skillet over medium high heat and saute onions in vegetable oil, stirring occasionally, until caramelized and most liquid has evaporated, about 20 minutes.
Set onions aside.
Remove brisket from oven after one hour and add caramelized onions and all remaining ingredients, moving meat around to combine ingredients.
Cover and continue to bake until very tender but not falling apart, another 2 to 3 hours.
Remove brisket to a carving board and slice.
Strain reserved cooking liquids and pour over sliced brisket.
Brisket may be returned to casserole dish and allowed to cool, then served the next day. (Reheated in oven.).