Place sliced onions into a large slow cooker. Top with beef broth, wine, worcestershire, butter, garlic, and rosemary.
Cook on low 6-8 hours or until onions or soft.
If desired, spoon into oven safe bowls and top with bread/croutons and Swiss cheese. Place in warm oven to melt cheese.
SNAPPY TIPS: Be sure you slice your onions thinly so that they cook evenly. The recipes makes a lot but you can easily cut the recipe in half or make a big batch and freeze in small containers.SNAPPY SUBSTITUTIONS: Instead of wine, you can substitute your favorite beer or omit for an alcohol free version. For a healthier version use low fat cheese or omit the cheese and bread.
Keywords: easy french onion soup, slow cooker soup