Rich and Creamy Four Cheese Soup

Melt butter in a large saucepan over medium heat. Add onion and cook about 5 minutes until tender, stirring occasionally. Add broth and potato and bring to a boil. Reduce heat and simmer soup 25 minutes, stirring occasionally. Puree soup in a food processor and return to the saucepan. Stir in half and half and bring soup to a simmer. Add Provolone, Parmesan, Mozzarella and Cheddar to the soup and whisk until melted. Divide soup between bowls and serve.