Super Skinny Spinach Soup

1. Melt butter in a large soup pot. Add onions and garlic and sauté until tender.
2. Sprinkle flour on top and cook for an additional minute. Then pour in chicken stock. Bring to a simmer, stirring well to remove any flour lumps.
3. Meanwhile, bring another large pot of water to a boil. Add spinach and blanch for about 30 seconds, just long enough to for it to turn a bright green. Immediately remove the spinach from the boiling water and put into an ice-bath to stop the cooking process.
4. Drain the spinach from the ice-bath, squeezing it with your hands to remove excess water. Put into a blender.
5. Add onion broth mixture to blender with spinach and puree until smooth. Season to taste with salt and pepper.
6. Garnish with heavy cream and croutons if desired.