Cut the bottom round steak into thin strips, around 1/8 inch thick, ensuring to slice across the grain.

In a sizable saucepan, mix together the beef stock and the stew seasoning.

Bring the mixture to a boil, then lower the heat to let it simmer for approximately one hour, keeping it covered.

While the beef is cooking, slice the red bell pepper and onion into manageable strips. Drain the canned mushrooms.

Heat a griddle or large frying pan with a bit of vegetable oil and cook the onions until they become translucent. Add the bell pepper strips and continue grilling until they are tender.

Just before the vegetables are fully cooked, add the mushrooms to the griddle and season with sea salt and ground pepper.

In a microwavable container, heat the Cheese Whiz for about a minute, stir, and then heat again until smooth and creamy.

To make the sandwiches, slice the bratwurst buns in half lengthwise and dip the cut sides into the beef broth for extra flavor. Optionally, toast the dipped sides on the griddle for a few moments.

Fill the bottom halves of the buns with the beef, followed by a generous helping of grilled peppers, onions, and mushrooms.

Drizzle the gooey Cheese Whiz generously over the top and serve.