In large saucepan, cook bacon over medium heat, stirring often, until crispy, 3 to 5 minutes. Using slotted spoon, transfer to small bowl. Cover; chill. Add onion to pan drippings. Cook, stirring often, until softened, 5 minutes. Add garlic; stir 1 minute. Add beans, stock, 1 tsp. salt and 1/2 tsp. pepper; bring to boil. Cover; reduce heat to low. Simmer until beans are soft, stirring occasionally, about 2 hours. Stir in vinegar; top with bacon.