Peel, rinse and slice the onions thinly and evenly. Finely chop or mince two garlic cloves and keep aside.
Place a heavy pan on the stovetop. Add butter.
When butter states melting, add the sliced onions with a pinch of salt.
Mix the onions with the butter really well.
Stirring often continue to sauté the onions on a low or medium-low flame till the onions caramelize.
Initially stir the onions after an interval of 2 to 3 minutes till they become light golden. When the onions turn light golden, then stir the onions continuously for even cooking and browning.
Once the onions have caramelized and have a nice golden color to them, add 2 tablespoons dry white wine.
Deglaze and remove all the stuck bits of caramelized onions from the bottom of the pan. Sauté for 1 to 2 minutes.
Now add flour. Mix very well and sauté for 2 minutes.
Then add the garlic and bay leaf. Mix well and sauté for a minute. If the onions start sticking to the pan, then sprinkle some water or stock.
Add the vegetable stock, 1 rosemary sprig. Also, season with salt and freshly crushed black pepper. stir and mix.
Salt is added as the veggie stock I had made, did not have any salt. If using stock with salt in it, then you can skip adding salt or add less of it.
Cover the pan.
Simmer for 30 minutes on a low flame.
You can check the soup while it is simmering after an interval of 10 to 15 minutes.
Toasting Bread or Baguette slices
When the soup is simmering, toast the slices of french bread or baguette or regular wheat bread or white bread. Slice the french bread.
Place the baguette slices on a baking tray. Brush with some melted butter or olive oil.
In a preheated oven toast bread slices at 230 degrees Celsius (450 degrees Fahrenheit) till light golden.
Pour soup in a baking safe soup bowls for individual servings or use a baking safe pot or pan.
Place toasted bread slices on the onion soup.
Sprinkle grated gruyere cheese all over the toasted bread slices.
Place the bowls in a baking tray. Keep the tray in a preheated oven and broil at 230 degrees Celsius (450 degrees Fahrenheit) till the cheese melts. Broiling means keeping the pan or tray beneath the top heating element of the oven. The top heating element should be used when baking.
Let cheese melt or become golden. Remove and serve hot garnished with some parsley or chives.
Baking Cheese toasts separately
For baking the cheese toasts separately top grated gruyere cheese on the toasted baguette slices.
Bake at 230 degrees Celsius (450 degrees Fahrenheit) in a preheated oven till the cheese melts.
Place the cheese toasts on the soup.
Serve hot. Garnish with some parsley or chives while serving.
Herbs: Herbs like rosemary or parsley can be skipped completely. Fresh thyme can also be added instead of rosemary.
Onions: Slice the onions thinly and evenly. You can use any variety of onions like red onions, white onions, yellow onions or shallots.
Vegetable stock: Avoid using packaged stock having a high sodium content. It is better to make vegetable stock and use it in the recipe.
Flour: You can either whole wheat flour or all-purpose flour.
On caramelizing onions: For the soup to have a truly authentic and great flavor, it is important to caramelize the onions really well. So use a heavy pan or pot. Stir often when sauteing the onions. Toward the end stage when the onions become light golden, you have to stir often so that the onions get an even golden color and do not burn or darken. So stirring and cooking onions on a low to medium-low flame is the key. Even a slight burning of the onions will ruin the entire soup.
Wine: You can use sherry wine or dry white wine. You can even use red wine. If you do not plan to add wine, then use vinegar. I suggest ½ to 1 tablespoon (depending on your taste) of white wine vinegar, red wine vinegar or apple cider vinegar.
Gluten-free option: For the bread, use a gluten-free bread.
Cheese: Apart from Gruyere cheese, you can also add a vegetarian Parmesan cheese.
Vegan option: Replace with a vegan butter or olive oil or neutral flavored oil and vegan cheese.