Start by slicing your onions sautee style or with the gain as it's called.

Cut the bell pepper into slices as well.

Slice the mushrooms and make sure to remove the woody stalk.

Heat the olive oil in your skillet and cook till they start to brown.

Add in your mushrooms and beef and sautee for a few minutes till you start to get some colour on the beef or fond at the bottom of the pan.

Deglaze with half the stock and mix everything well.

Add in the green bell peppers and season with salt, pepper, paprika and garlic powder.

Cook for another minute before adding in the cream cheese, cheddar cheese and remained of the stock.

Now you want to mix everything well and cook till you have a creamy sauce

Depending on how 'moist' you want your sandwich cook out the liquid in the pan. If there is lots turn the heat up and reduce it to your liking.

Chop the parsley and sprinkle on the beef in the pan and give it a final good mix.

Now use the sandwich filling as desired.