Creamy Garlic Spinach Soup

1/2 pound fresh spinach
8 tablespoons butter, divided
3 cups chicken stock
4 medium potatoes, diced
2 large garlic heads, minced
2 large onions, diced
2 cups heavy cream
2 large egg yolks

Rinse spinach and shred with knife; set aside.

Heat six tablespoons butter in a 2 quart soup pot and cook onion until tender. Add chicken stock and diced potatoes. Cook on medium heat for 30 minutes. If you like, you may allow potatoes to disintegrate or you may crush them as they cook. Add minced garlic, onions and spinach. Simmer for another 10 minutes. Add cream and simmer on low.

In a small bowl, add 1/2 cup of soup to 2 egg yolks, in a stream while whisking, taking care not to curdle the yolks by adding the hot soup too quickly. Add whisked mixture to the soup pot, stirring constantly until the soup is thickened. Add salt and pepper to taste. Remove from heat and swirl in remaining butter. Serve immediately with crusty garlic bread.