If at all possible, use stone-ground grits for this recipe. They require additional cooking time, but the taste and texture are worth it.
Mix first four ingredients in a small bowl. Place meat between sheets of waxed paper and, using a mallet, flatten each piece slightly. Remove top layer of paper, dip mallet into garlic mixture (or sprinkle a small amount over each piece of meat) and pound the mixture into meat. Turn meat over and repeat on second side (meat should double in size during the pounding process). Rub meat lightly with flour.
Heat butter and oil in a Dutch oven over medium-high heat. Add meat in small batches and saute until browned. Do not overcrowd the pan, or meat will steam, rather than brown. Transfer to plate. Add onion, celery, green pepper, tomato paste and water to pot, stirring to combine. Return meat to pot, add any remaining garlic mixture and vinegar and simmer, covered, until tender (about one hour). Season to taste and serve over grits. 6 servings.