Peel and halve onions through the core and slice the halves in ¼" wedges, removing the core at the root end.
Heat the vegan butter, split between two skillets or heavy pans, over medium heat. Add the onions to the pans and season with the sea salt. Using a couple of wooden spoons, toss the onions to evenly coat them in the vegan butter.
Stir the onions occasionally to ensure that they are not sticking and to evenly cook all of the onions.
As the onions begin to release water and brown or caramelize, you will need to reduce the heat to medium-low and stir more often. If necessary, sprinkle a little water in the pans to prevent sticking and burning.
While the onions are caramelizing, heat your vegetable broth and prepare your fresh thyme and bay leaves. As indicated in the post, homemade vegetable broth results in the best flavour.
After caramelizing the onions for at least an 1 hour, but up to 1 hour 15 minutes, deglaze the skillets for about 5 minutes, with the wine split between the two pans.
Transfer the contents of the skillets to a heavy soup pot or dutch oven and add the warmed vegetable broth, fresh thyme, bay leaves and Worcestershire sauce, if using.
Bring the soup to a simmer and cover for approximately 30 minutes before tasting.
You can portion the soup into individual soup bowls and top with toasted rounds of baguette and vegan cheese and place these under a broiler to melt the cheese. Alternatively, you can place the toasted baguette rounds and cheese atop the soup in the pot and place this under the broiler. Simply serve the soup from the pot with a ladle, into bowls as soon as it is ready.