The first thing you must understand is the culinary principle of only adding a wine to your food that you wouldn’t mind drinking on its own. Marsala is wine, after all, even though it's fortified and the sauce takes a healthy does that truly affects the end result.
Make sure to have your hardware ready when you begin. I like to use a large roasting pan spanned across two burners for this preparation. Also have a sheet pan with drying rack, to put the scaloppini on, after they are cooked.
2 shallots (fine dice)
1 Tbls. Fresh sage (fine dice)
1-pound cremini mushrooms (washed and sliced)
1 ½ cups Dry Marsala (look for a good brand)
1-¼ cups chicken stock
1 ½ Tbls. fresh parsley (minced)
Salt and pepper for seasoning
2-½ pounds pork tenderloin, chicken breast or veal (cut and tenderized into scaloppini about ¼ inch thick)
1 cup all purpose flour
4 Tbls. butter
6 Tbls. olive oil
Season the cutlets lightly, on both sides, with salt and pepper. Then coat them in flour. Make sure to shake off any excess flour.
In a roasting pan (spanned across two burners on medium heat) add 4 Tbls. of olive oil and 2 Tbls. of butter. Allow the butter and olive oil to come up to temperature. Watch as the butter begins to foam. Once the foaming has settled (that’s the water cooking out), you can begin to add the cutlets, one at a time. If you can’t fit all the cutlets comfortably into this pan then cook off the second batch separately. Turn the cutlets once they have formed a good sear on one side. When both sides have been seared, remove the culets from the oil and rest them on a sheet pan.
Drain all the fat from the roasting pan and add 2 Tbls. olive oil and 2 Tbls. of butter. As the oil and butter come up to temperature, scrape the bottom of the pan to loosen the cooked on bits from the cutlets (the fond).
Cook the mushrooms and stir regularly for about five minutes. The mushrooms should begin to shrink, and the liquid they release will cook off.
Now raise the heat to medium-high and add the Marsala. Bring it up to a boil and let it reduce for about a minute.
Taste and season with salt and pepper.
Lastly, add the cutlets back into the pan and allow them to warm in the sauce as it continues to reduce. Flip them after a minute and, once you see that they are taking on a slight glaze from the sauce, turn off the heat. Add about half of your chopped, fresh parsley and stir it into the sauce.