Wash and trim fresh beans, if using. Cook, covered, in very large saucepan with a small amount of boiling water for 20 to 25 minutes or until crisp-tender. (Cook frozen beans according to package directions.) Drain beans; rinse with cold water and set aside.
Meanwhile, cook bacon in skillet until crisp. Remove bacon from pan, reserving drippings in skillet. Drain bacon on paper towels, crumble, and set aside. Cook onion and garlic in drippings over medium heat for 3 minutes or until tender. Stir in mustard, seasoning or pepper, and salt. Cook about 30 seconds more. Toss beans with onion mixture; heat through. Sprinkle with bacon. Makes 12 side-dish servings.
Cook beans to crisp-tender and refrigerate, tightly covered, up to 8 hours. To serve, cook bacon and proceed with recipe.