Melt your unsalted butter in the large heavy bottomed pot over medium heat. Do not let the butter turn brown or burn.

Add all your thinly sliced white onions to the melted butter carefully. Stir them well to coat every piece with butter.

Turn the stove to medium low heat now. Cook the onions slowly for about twenty five minutes. Stir them occasionally so they do not stick.

Sprinkle your all purpose flour over the soft onions evenly. Cook and stir this mixture for exactly two minutes. This removes the raw flour taste.

Pour your warmed vegetable stock into the pot very slowly. Whisk the liquid constantly to avoid any flour lumps.

Drop your bay leaves into the pot now. Bring the liquid to a gentle boil over medium heat.

Reduce the heat to low. Let the soup simmer uncovered for fifteen minutes to blend the flavors.

Remove the bay leaves from the pot carefully. Use your immersion blender to puree the soup until it is completely smooth.

Stir in your room temperature heavy cream gently. Season the smooth soup with salt and white pepper according to your taste.

Ladle the hot soup into warm bowls. Serve it immediately while it is fresh and creamy.