First, slice the onions thinly and mince the garlic.
Then, add the vegan butter to a large dutch oven or saucepan and turn on the heat.
Once the butter has melted add in the sliced onions. Stir to coat with the butter and saute for 25-40 minutes over medium heat until the onions are browned and caramelized. It's important to stir the onions consistently so they cook evenly and do not burn. For even more flavor, cook the onions for 1-2 hours at a very low heat until they are a deep brown color.
Next, add the minced garlic and the seasoning including the dried parsley, salt, pepper, and dried thyme to the pot. Saute with the onions for another 2-3 minutes.
Pour the white wine into the pot to deglaze the pan and remove any stuck bits from the bottom. Then cook with the onion and garlic for another 2 minutes.
Next, add in the mushroom broth and vegan worcestershire sauce. Stir everything together and bring the soup to a boil.
Once boiling, reduce the heat to a simmer, add the lid, and cook the soup for another 10 minutes. While the soup is simmering, toast your slices of bread.
Remove the soup from the heat and add the broth to 4 oven safe bowls. Top each bowl with a slice of toast and a healthy dose of vegan cheese (about 2 Tablespoons per bowl). Then, place the bowls on a baking tray and add to the oven to broil for about 5 minutes or until the cheese is begining to bubble and brown.
Remove the tray of soup bowls from the oven, garnish with fresh thyme, and serve while hot.