1. In a large pot, melt the butter over medium heat. Sautee the onions in the butter as the butter melts for a minute or so then add the rest of the ingredients (besides the toppings).
2. Bring to a boil then reduce heat to simmer uncovered for 30-40 minutes or until the onions are soft.
3. Blend until smooth in a regular blender or with an immersion blender. Add additional salt and pepper as needed. Eat plain (also wonderful) or garnish with parmesan and basil.