Preheat the oven to 400 degrees Fahrenheit.
Season the pork loin with mustard, followed by the Italian seasoning, salt, pepper, onion powder, garlic powder, and smoked paprika.
In a large pan, heat the oil over medium-high heat. Sear the pork in batches for 3-4 minutes per side, or until golden brown. Don’t worry if some seasoning falls off; it will add flavor to the sauce.
Transfer the seared pork to a baking sheet lined with a wire rack. Once all the pork is seared, reduce the heat to low and add 4 tablespoons of butter, minced garlic, and ½ cup of broth or water to the pan.
Place the pork in the preheated oven and bake for 20-25 minutes, checking the temperature halfway through. For medium-rare pork, it should reach a temperature of 145-150°F, medium 150-155°F, and medium-well 155-160°F.
Once the pork reaches your desired temperature, remove it from the oven and place it on a cutting board. Loosely cover the pork with foil and let it rest for 10 minutes before slicing.
Meanwhile, bring the butter and water/broth in the pan to a low simmer, scraping the bottom of the pan to incorporate all the browned bits.
Add the remaining ingredients for the sauce except the Parmesan cheese. Taste and adjust seasoning as needed.
Once the seasoning is adjusted to your liking, turn off the heat and stir in the grated Parmesan cheese.
Slice the rested pork loin and top it with the Parmesan mustard cream sauce. Serve with extra Parmesan cheese on the side.
Enjoy your Italian Pork Loin with Parmesan Mustard Cream Sauce!