Peel off and chop the onions, and sauté in melted butter for 15 minutes, stirring continuously on medium heat.
When the onion is soft, add the minced garlic. Stir well and when fragrant, add the flour and stir until it gets golden-brown.
Pour in the broth, bring to the boil, add the bay leaves and simmer for 15 minutes.
Meanwhile preheat the broil.
Mix the soy cream, nutritional yeast and fleur de sel. Spread on the bread slices and grill for 2-3 minutes.
Add the milk to the soup and serve with the bread slices au gratin.