Place the chicken breasts onto baking paper, then cover with a few folded over layers of cling film. Bash each one with a rolling pin or a tenderising hammer until they are 0.5 cm thick.
Add the eggs into a bowl and beat them with a fork, in a separate bowl add the flour, garlic salt and paprika, mix it well.
Dip the chicken in the beaten egg, then coat it in the seasoned flour.
Heat a good amount of oil in a large frying pan, cook the chicken over a medium to high heat for a few minutes on each side until it's golden and cooked through.
Remove the chicken from the pan and set it aside. Get rid of most of the oil if there's any left in the pan.
Chuck in the butter, once it starts to brown add in the sliced onion. Cook the onions for a few minutes until they start to soften.
Add the garlic and mushrooms and stir well. Keep cooking for a few more minutes.
Pour in the Marsala wine and bring to the boil, simmer for a few minutes.
Now pour in the chicken stock and add the chicken back into the pan. Let it simmer for a few more minutes.
Add in the double cream and simmer until it starts to thicken. Season to taste and then finish with the chopped parsley.