Slice the steak, mushrooms and pepper thinly. Set aside.
Slice the onion thinly; set aside. Chop up the garlic, or crush it.
Heat the oil in a large frying pan, and cook the onion and garlic in the oil until softened.
Add the mushrooms, steak and pepper, and stir fry for 5 minutes. Add the snow peas, yoghurt, white wine and parsley, and season with salt and pepper. Cook until heated through.
Serve hot.
Notes
Easily doubled or tripled. For a zestier sauce, try adding a teaspoon of mustard. You can also try adding pinches of sage, oregano, etc.