In a large pot, bring water and salt to a boil. Add the broccoli and cook for about 5 minutes, or until the broccoli is tender. Be careful not to overcook it, as you want to retain its vibrant green color.
Drain the cooked broccoli and transfer it to a blender or food processor. Blend until smooth. If you prefer a chunkier soup, you can reserve a few broccoli florets and set them aside.
In the same pot used to cook the broccoli, sauté the onions until they become translucent and slightly caramelized.
Add the blended broccoli to the pot with the sautéed onions. Stir in the heavy cream and season with salt, pepper, and garlic to taste. If you reserved some florets earlier, add them now for added texture.
Bring the soup to a simmer over medium heat, stirring occasionally. Allow it to cook for about 10 minutes, or until it thickens slightly and the flavors meld together.
Taste and adjust the seasoning if needed.
Remove the pot from the heat and let the soup cool slightly.
Serve the broccoli soup hot, garnishing it crispy onions or shredded cheese.
