What happens next?

How to make cheeseburger soup
Preheat the oven.
To toast the hamburger buns for the crouton topping, the oven must be hot enough. Set the temperature to 400 degrees fahrenheit (200 degrees celsius), and allow it to fully preheat.
If you prefer, you can toast the buns in a toaster oven rather than a standard oven. Spread the bun pieces out on a baking sheet.