Slice chicken breasts in half (lengthways).
Mix garlic powder, mixed herbs and pepper. Season chicken breasts with the mixture.
In a large frying pan, melt the butter and fry the chicken breasts, 5-6 minutes on each side or until cooked through. Set aside.
Add mushrooms and onion to frying pan and fry until tender and slightly browned. Add garlic and fry for another minute.
Stir in the thick cream, herbs and parmesan simmer until sauce thickens.
Return chicken to the pan, cook for 4 - 5 minutes.