Place the Porcini mushrooms in a jug and cover with hot water (see pic 1). Set aside and leave for 15 minutes before using.
Chop up the button mushrooms and the shallots and garlic and set aside.
Slice horizontally through the chicken breast (see pic 2). You do not need to do this if the chicken breasts are small.
Using a rolling pin or tenderiser, pound the chicken breasts until they are approx ½ cm thickness (see pic 3). NB - if you use a wooden rolling pin to pound the chicken it is very important to clean it thoroughly afterwards.
Put the flour in a large freezer bag and add 4 - 5 grinds of salt and pepper. Place the chicken breasts in the bag and shake so that the chicken is covered with flour (see pic 4)
Heat the oil and half of the butter in a frying pan / skillet over a medium high heat.
Place the chicken breasts in the pan and fry, turning once, until the chicken is golden and is just about cooked through. This will probably take 6 - 7 minutes.
Turn off the heat, remove the chicken from the pan, place on a plate and set aside.
Remove the Porcini mushrooms from the water and roughly chop up. Keep the water that the mushrooms have soaked in as you will use some of this for the sauce.
Melt the remainder of the butter in the frying pan / skillet and add the chopped Porcini mushrooms and button mushrooms and stirring continuously cook for 4 - 5 minutes until they start to brown (see pic 7).
Use a wooden spoon to scrape any browned bits from the bottom of the pan (these will add to the taste of the sauce).
Add the chopped shallots and garlic and cook for an additional 2 - 3 minutes continuing to stir so that things don't stick.
Now you want to add the chicken stock, 80 ml of the water that the Porcini mushrooms were soaking in, a little salt and pepper and the Marsala.
Bring the sauce to the boil and then reduce the heat so that the mixture is simmering.
Cook for 10 minutes until the liquid has reduced by about half.
Add the chicken breast to the mushroom sauce and cook over a low heat until the chicken has cooked through (this should only take another 5 - 8 minutes).
Serve sprinkled with chopped parsley (see pic 9)