Trim the excess fat off pork (if desired) and cut it into 1" medallions. Season each piece with salt & pepper.
Add the oil and one tablespoon of the butter to a skillet over medium-high heat. Let the pan warm up for a few minutes.
Sear the pork for 3 minutes/side then transfer it to a plate.
Add in the remaining 2 tbsp butter and once it melts, add in the mushrooms and cook for 5-6 minutes, stirring occasionally, or until the water has been released and cooked off.
Stir in the garlic, Dijon mustard, Italian seasoning, and chicken broth. Let it bubble for about a minute.
Add in the cream and let it bubble for about a minute.
Add the pork back into the pan and let it cook for another 3-5 minutes or until the pork has cooked through and the sauce has reduced/thickened a bit. You may need to turn the heat down a bit so it doesn't boil furiously.
(optional) If you want thicker sauce, add in the corn starch that has been mixed with a ¼ cup of cold water and let cook for a mintue or two more.
Season with extra salt & pepper as needed and serve immediately.