Heat the oil in a frying pan over medium heat.

Sauté the onion, stirring frequently, for three to five minutes or until it has begun to soften and become translucent.

Add the mushrooms and peppers and cook, stirring frequently, until they begin to soften.

Sprinkle the flour over top of the vegetables and stir through.

Cook for a minute or so, stirring constantly.

Stir in the chicken stock, stirring constantly until it begins to thicken.

Add the milk, a bit at a time, stirring after each addition until the sauce thickens. Do this until you have a lovely creamy sauce.

Add the Worcestershire sauce or sherry and stir to mix through.

Stir in the meat and the frozen peas.

Cook for about four minutes, stirring frequently, until the meat heats through and the peas are cooked. Add a bit more milk if the sauce becomes too thick.

Taste for seasoning and add salt and pepper if necessary.