Remove the pork tenderloins from the refrigerator 20 to 30 minutes before cooking. Trim away the silver skin and excess fat, then pat the pork dry with paper towels.
Preheat the oven to 400°F. Place a wire rack over a foil-lined baking sheet and set aside.
In a small bowl, combine the kosher salt, black pepper, garlic powder, onion powder, smoked paprika, and dried thyme. Rub the pork tenderloins with the olive oil, then coat them evenly with the seasoning mixture.
2 tablespoons olive oil, 2 teaspoons kosher salt, 1 teaspoon coarse black pepper, 1 teaspoon garlic powder, 1 teaspoon onion powder, 1 teaspoon smoked paprika, 1 teaspoon dried thyme, 2 lb pork tenderloin
Heat a large skillet over medium-high heat. Add the pork tenderloins and sear for 2 to 3 minutes per side, turning until deeply browned on all sides.
Transfer the seared pork tenderloins to the prepared wire rack. Roast uncovered for 15 to 20 minutes, or until an instant-read thermometer inserted into the thickest part of each tenderloin reads 140 to 143°F.
As soon as the pork goes into the oven, return the skillet to medium heat. Melt 2 tablespoons of the butter into the browned bits left from searing the pork.
3 tablespoons unsalted butter
Add the shallots and cook for 2 to 3 minutes, stirring occasionally, until softened. Add the garlic and cook for 30 seconds, just until fragrant.
2 small shallot, 5 cloves garlic
Pour in the chicken broth and scrape up the browned bits from the bottom of the skillet. Bring to a boil and cook until the broth has reduced by about half.
1 1/2 cup low-sodium chicken broth
Reduce the heat to medium-low. Whisk in the heavy cream, Dijon mustard, Worcestershire sauce, and thyme. Simmer gently, stirring occasionally, until the sauce thickens enough to coat the back of a spoon.
1 cup heavy cream, 4 tablespoons Dijon mustard, 1 1/2 teaspoon Worcestershire sauce, 1/2 teaspoon dried thyme
Remove the skillet from the heat. Stir in the lemon juice, then whisk in the remaining 1 tablespoon cold butter until melted and smooth. Fold in the chopped parsley and season to taste with kosher salt and freshly cracked black pepper.
3 tablespoons unsalted butter, 1 teaspoon fresh lemon juice, 2 tablespoons chopped fresh parsley, Kosher salt and freshly cracked black pepper
Transfer the cooked pork tenderloins to a cutting board and loosely tent with foil. Let them rest for 10 minutes. The internal temperature will continue to rise to about 145°F.
Slice the pork tenderloins into ½-inch medallions. Spoon the warm Dijon pan sauce over the pork and garnish with additional parsley, fresh thyme leaves, and freshly cracked black pepper, if desired.