Preheat the oven: Preheat your oven to 400°F (200°C).

Season the pork tenderloin: Rub the pork tenderloin with olive oil, garlic, rosemary, thyme, Dijon mustard (if using), salt, and pepper. Let the pork sit for 10 minutes to absorb the flavors.

Sear the pork: In a large oven-safe skillet, melt the butter over medium-high heat. Sear the pork tenderloin on all sides for about 2-3 minutes per side, until golden brown.

Roast the pork: Transfer the skillet with the pork tenderloin to the preheated oven and roast for 15-20 minutes, or until the internal temperature reaches 145°F (63°C).

Deglaze the pan: Remove the pork from the skillet and let it rest. Add chicken broth to the skillet, scraping up the browned bits from the bottom of the pan. Let the broth simmer for 2-3 minutes, then pour the sauce over the pork.

Serve: Slice the pork tenderloin and serve with the garlic herb sauce, garnished with fresh parsley.