There are many recipes for French onion soup. However,THIS recipe comes closest to the flavour of Panera's recipe, both in flavour and in texture.
You will need-
4 Large White Onions, thinly sliced
1/3 Cup butter
24 oz Low Sodium Beef Broth
1 cup Low Sodium Chicken Broth
12 oz Water
3 Tablespoons Flour
2 Tablespoons Ketchup
2 Teaspoons Salt
2 Teaspoons Ground Black Pepper
1/2 Teaspoon Thyme
1 Large Clove Crushed Garlic
Dash of Cayenne Pepper
Toppings-
Asiago Cheese and Parmesan Cheese, either thinly sliced or shaved. Large croutons either homemade, or purchased. For "authentic" Panera croutons, use their Focaccia, slice the bread 1 inch thick, butter both sides and cut into large chunks. Toast the bread on a cookie sheet at 400 degrees Fahrenheit, for 12-15 minutes, until crunchy.
To make the soup-
In a large saucepan,on medium heat, melt the butter. Add the onions and saute until dark brown and carmelised. Next add the remaining ingredients, and stir until well combined. Bring the soup to a boil. Reduce heat and simmer uncovered, for 20-30 minutes. Stirring occasionally. Serve topped with the croutons and the cheese.
This will make about 6 servings.
Note- For the cheese topping, use slightly more Asiago than Parmesan.