Preheat your oven to 400°F (200°C).

In a small skillet over medium heat, toast the anise seeds for about 2-3 minutes until fragrant. Remove from heat and let cool.

In a small bowl, combine the toasted anise seeds, lime zest, salt, and black pepper. Mix well to create a spice crust.

Rub the top sirloin steak with olive oil on all sides.

Press the spice mixture evenly onto the surface of the steak, ensuring it's well coated.

Heat a large, oven-safe skillet over medium-high heat. Once hot, sear the steak for 4-5 minutes on each side until a golden crust forms.

Transfer the skillet to the preheated oven and roast for about 10-15 minutes, or until the internal temperature reaches your desired doneness (135°F for medium-rare).

While the steak is roasting, prepare the horseradish-mustard compound butter. In a medium bowl, combine softened butter, horseradish, Dijon mustard, and mix until well blended. Set aside.

Once the steak is done, remove it from the oven and let it rest for 5-10 minutes before slicing.

Serve the sliced steak topped with a dollop of horseradish-mustard compound butter and garnish with chopped parsley if desired.