Place bacon in a medium-sized saucepan and heat over medium high. Cook until bacon is done the way you like it, and remove to drain on paper towels. Carefully pour out bacon drippings and return saucepan to the stove.
Add chicken broth and heat to a simmer. Stir in spinach until wilted. Stir in cheese.
Drizzle beaten egg into the soup, stirring for about 30 seconds. The egg will form little feathery strands.
Season to taste with salt and pepper and ladle into bowls. Garnish with bacon and serve.