Slice pork tenderloin into about 1/2 inch-thick slices. Lay slices on the cutting board and sprinkle with some salt and fresh cracked pepper.
Preheat a large cooking pan on medium-high heat and add some oil. (Make sure the pan is nice and hot before adding pork.) Place pork slices in the skillet and sear on both sides until you get that nice golden brown sear. Take out pork.
In the same skillet, lower heat to medium and add sliced mushrooms. Saute mushrooms for a couple of minutes and add Marsala wine.
Simmer for a few minutes and then add heavy whipping cream. Stir well.
Add green onion, some salt and thyme. Stir well.
Add pork slices back to the pan with sauce. Cook until pork is done. (Cook time may vary depending on how thick you cut your pork. Estimate time, 10-15 minutes after adding pork back to the pan. Cut into the thickest slice to make sure it's done.)