Heat a large cast iron skillet on medium heat, heat the olive oil. Cook the pancetta until crisp and then remove it to a plate.
Add the butter and cook the shallot on medium heat until tender. Add the mushrooms and cook until browned and all the liquid has evaporated. Remove from the pan and cover to keep warm.
Now add the vegetable oil to the pan. Sprinkle the pork with the salt and pepper and then dredge it in the flour. Cook half the pork on medium heat in the oil on both sides until it's brown and cooked through. It should be 140 degrees inside and will continue to cook outside of the pan. Repeat with the rest of the pork. Remove it to a serving platter and cover to keep warm.
To the pan add the tomato paste and garlic and cook for one minute. Remove the pan from the heat. Add the Marsala and simmer until it's reduced by half. While it simmers, scrape the bottom of the pan. Stir in the cream and simmer for five minutes on low heat. Add the rest of the salt and pepper, and the lemon juice and parsley. Also, add the pancetta, mushrooms, and pork back to the pan. Cook for one minute and then serve.