This is a great way to use up leftover roast beef, flank steak, whatever you have around. If you plan ahead, save some gravy for this. If you don't have any leftover gravy, you can use some of the instant stuff, although I prefer this recipe for "gravy on the fly."
4 potatoes, peeled, and diced
1-2 cups leftover chopped beef
1 cup gravy
1 onion, diced
salt and pepper to taste
If the potatoes are raw, start to brown them in some olive oil and butter. If you're using leftover potatoes, just dice them and then add the other ingredients.
When the potatoes are done, add the beef, gravy, and onion and cook until browned, stirring now and then. Taste and add salt and pepper as needed.