Dutch Oven French Onion Soup

First, peel and slice all of the onions thinly.
Melt one stick of the butter in a dutch oven pot over medium heat on the stovetop.
Toss the onions to coat them in the butter and then add the salt, pepper and red wine vinegar.
Cook the onions, stirring frequently, for 40-50 minutes until they are completely softened and a deep brown color.
While the onions are cooking, slice the baguette into one inch slices and place them on a baking sheet lined with parchment paper.
Spread the baguette slices with the softened butter and sprinkle with the garlic salt.
Place the baguette slices under the broiler in the oven for 2-3 minutes until they are lightly browned and toasted.
When the onions are done cooking, add the white wine to deglaze the pot. Use a wooden spoon to scrape the bottom of the pot to loosen any stuck on browned bits.
Stir in the beef broth and add the fresh thyme bundle. Bring the soup to a boil over medium high heat and then lower the heat to medium low and let the soup simmer for 10 minutes.
Top the finished soup with half of the toasted garlic croutons and sprinkle the gruyere cheese on top.
Place the dutch oven under the broiler in the oven for 3-4 minutes until the cheese melts and is slightly browned.
Serve the soup hot with the remaining garlic croutons for dipping.