Prepare the Steaks: Take the top sirloin steaks out of the refrigerator and let them sit at room temperature for about 30 minutes. This helps them cook evenly. Preheat your grill or cast-iron skillet over medium-high heat.

Season the Steaks: Rub each steak with olive oil and season generously with salt and black pepper.

Char the Shallots: In a small skillet, heat 1 tablespoon of olive oil over medium heat. Add the sliced shallots and cook until they are soft and charred, about 5-7 minutes. Stir occasionally to avoid burning. Remove from heat and let cool slightly.

Make the Tarragon Crust: In a mixing bowl, combine the charred shallots, chopped tarragon, and a pinch of salt and pepper. Mix well.

Cook the Steaks: Place the seasoned steaks on the hot grill or skillet. Cook for about 4-5 minutes on one side, then flip and cook for an additional 4-5 minutes for medium-rare, or adjust cooking time to your preference.

Prepare the Mustard-Seed Butter: While the steaks are cooking, in a small bowl, mix the softened butter, Dijon mustard, mustard seeds, and lemon juice until well combined.

Add the Crust: During the last minute of cooking, top each steak with the shallot and tarragon mixture, pressing it down gently.

Rest and Serve: Remove the steaks from the heat and let them rest for about 5 minutes. This allows the juices to redistribute. Serve the steaks with a dollop of mustard-seed butter on top.