Buy very thin slices of beef, or if you have your own piece of meat, cut thin slices yourself.
The first step is to boil the beef broth on medium heat in a pan.
Now you need to add ketchup, minced garlic and sliced onions along with onion and garlic powder.
When the broth is boiled, it is time for you to add the sliced roast beef.
Do not keep the roast beef in the broth for more than three minutes, as it is only done to allow the beef to absorb some of the broth's flavor.
Take the beef slices out and put the broth back on the stove and increase the heat.
Sprinkle Wondra flour over the surface, but do not forget to stir to avoid lumps.
Heat for about five more minutes and then introduce the mushrooms.
Now go back to the beef slices and put them on a slice of bread.
By this time the broth will be cooked, so pour it over the roast beef, add a tomato, some salt and pepper according to your taste.
You can serve it with French fries, cheese or milkshake on the side.