Heat the butter in a skillet over medium heat
Add the onion and sauté until translucent
Place the sliced mushrooms in the pan and brown for about 5 minutes, stirring 2 or 3 times
Pour in the broth and the white wine, and cook for about 5 minutes.
Add 1/2 cup of the half-and-half or cream. Bring the mixture to a boil, then lower the heat and simmer for about 3 minutes.
In a small separate bowl, mix the remaining 2 tablespoons of half and half with the 2 tablespoons of flour (making a slurry, or roux).
Add the roux to the mushroom mixture and bring it again to a boil, stirring to avoid lumps.
Add the chopped parsley and season with salt and pepper to taste.
Turn off the heat and cover the pan to keep the sauce warm while the pork cutlets are cooking.