Preheat your oven to 400°F (200°C).

Prepare the roasted garlic: Cut the top off the head of garlic to expose the cloves. Drizzle with olive oil and wrap in aluminum foil. Roast in the oven for about 30-35 minutes until soft and caramelized.

While the garlic is roasting, prepare the beef tenderloin. In a small bowl, combine the chopped scallions, grated ginger, salt, black pepper, and Dijon mustard. Mix well to form a paste.

Rub the scallion and ginger paste all over the beef tenderloin, ensuring it is evenly coated.

In a large oven-safe skillet, heat 2 tablespoons of olive oil over medium-high heat. Sear the beef tenderloin on all sides until browned, about 3-4 minutes per side.

Remove the skillet from the heat and sprinkle the toasted walnuts evenly over the top of the beef, pressing them gently into the crust.

Transfer the skillet to the oven and roast for about 20-25 minutes for medium-rare, or until the internal temperature reaches 130°F (54°C). Adjust cooking time according to your preferred doneness.

While the beef is roasting, prepare the gravy. Once the garlic is done roasting, squeeze the softened cloves into a saucepan. Add the beef broth, butter, and flour. Whisk over medium heat until the mixture thickens, about 5-7 minutes.

Stir in the soy sauce and season with salt and pepper to taste. Keep warm until ready to serve.

Once the beef is done, remove it from the oven and let it rest for 10 minutes before slicing.

Serve the sliced beef tenderloin drizzled with the silky roasted garlic gravy and garnish with fresh herbs if desired.