Follow these easy steps to make the Best-Ever Pork Tenderloin with Creamy Dijon Sauce:

1. Prepare the Pork: Preheat your oven to 400°F (200°C). Pat the pork tenderloin dry with paper towels and season generously with salt and pepper.
2. Sear the Meat: In an oven-safe skillet, heat the olive oil over medium-high heat. Once hot, add the pork tenderloin, searing on all sides until golden brown (about 3-4 minutes per side).
3. Remove and Set Aside: Once seared, remove the pork from the skillet and set it aside on a plate.
4. Sauté Aromatics: In the same skillet, add the chopped onion and cook until translucent, about 2-3 minutes. Stir in the minced garlic and cook for an additional 1 minute.
5. Deglaze the Pan: If using, add white wine or chicken broth to deglaze the pan, scraping up any brown bits. Let it cook for 1-2 minutes until slightly reduced.
6. Make the Sauce: Pour in the heavy cream, then whisk in the Dijon mustard and whole grain mustard until fully combined. Season with salt and pepper to taste.
7. Return the Pork: Place the seared pork tenderloin back into the skillet with the sauce. Spoon the sauce over the pork.
8. Roast: Transfer the skillet to the preheated oven. Roast for approximately 15-20 minutes or until the internal temperature of the pork reaches 145°F (63°C).
9. Rest the Meat: Once cooked, remove the pork from the oven and let it rest for about 5 minutes. This allows the juices to redistribute.
10. Slice and Serve: Slice the pork tenderloin into medallions, serving them drizzled with the creamy Dijon sauce. Garnish with freshly chopped parsley.

By following these steps, you will create an amazing dish that is both flavorful and tender.