- Prick the potatoes all over with a fork and place on a plate. Cook in the microwave oven for 6 to 8 minutes or until tender, turning halfway through cooking. Set aside.
- In non-stick skillet over medium-high heat, brown the mushrooms, onion and bell pepper in half of the butter. Season with salt and pepper. Keep warm.
- In another non-stick skillet over high heat, brown the beef in the remaining butter. Season with salt and pepper. Add to the vegetables.
- Place the potatoes in the hot skillet that was used for cooking the beef. With a potato masher, crush the potatoes down until ¾ inch (2 cm) thick. Deglaze the skillet with the broth and mustard. Sprinkle the potatoes with the cheese. Reduce the heat to low. Cover and cook for 3 minutes or until the cheese has melted.
- Serve the potatoes over the vegetables and beef. Garnish with sour cream and a knob of butter, if desired.
This recipe doubles easily.