Over medium heat, warm up the cooking oil in a large sauce pan
Add the onions, thyme and salt and lower the heat to medium low. Cook uncovered and stir occasionally for approximately 50 minutes, until the onions have caramelized
Add the balsamic vinegar and the Worcestershire sauce, stir and cook until fully absorbed (approximately 15 minutes)
Ad the vegetable brother, parsley, smoked paprika and pepper and bring to a boil. Turn the heat to low and simmer for 30 minutes
Prepare 4 oven-safe bowls and fill them 2/3 full with the soup. Add a slice of toasted bread on each and top with grated cheese.
Broil 5 minutes or until golden brown.