Start by combining the minced garlic, chopped rosemary, thyme, parsley, salt, and pepper in a small bowl. This fresh herb blend is the secret to the fragrant crust that will coat your tenderloin and infuse every bite with aromatic flavor.
Pat the beef tenderloin dry with paper towels to ensure a good sear. Rub the olive oil all over the surface of the meat. Season generously with salt and pepper. Heat a large oven-proof skillet over medium-high heat. Once hot, sear the tenderloin on all sides until it develops a golden-brown crust, about 2-3 minutes per side. This locks in the juices and creates a beautiful base for the herb crust.
Remove the skillet from heat. Using a brush or spoon, spread the Dijon mustard evenly over the seared tenderloin. Then, press the herb mixture onto the mustard-coated beef, making sure it adheres well and covers the entire surface.
Preheat your oven to 400°F (200°C). Transfer the skillet with the tenderloin into the oven and roast for about 20-25 minutes, or until the internal temperature reaches 130°F (54°C) for medium-rare. Use a meat thermometer for precision. Once done, remove the tenderloin from the oven and tent it loosely with foil. Let it rest for 10-15 minutes to allow the juices to redistribute.
While the beef rests, place the skillet back on the stovetop over medium heat. Carefully add the beef broth and balsamic vinegar to the pan drippings, scraping up any browned bits with a wooden spoon. Simmer for 5 minutes or until the sauce has reduced slightly and thickened. Adjust seasoning if needed.
Slice the rested beef tenderloin into thick medallions. Drizzle the pan sauce over the slices or serve it on the side. This dish pairs beautifully with roasted vegetables, creamy mashed potatoes, or a crisp salad.