Pat the hanger steak dry with paper towels. In a small bowl, mix together the smoked paprika, salt, and black pepper. Rub this spice mixture all over the steak.

In a separate bowl, combine the chopped spring onions and fresh rosemary. Add olive oil and mix until the onions and rosemary are well-coated.

Preheat a grill or a cast-iron skillet over medium-high heat. Once hot, place the steak on the grill or skillet. Cook for about 3-4 minutes on each side for medium-rare, or adjust cooking time to your desired doneness.

While the steak is cooking, melt 4 tablespoons of butter in a small saucepan over low heat. Add the minced garlic and Szechuan peppercorns, cooking gently for about 2-3 minutes until fragrant. Do not let the garlic brown.

Once the steak is nearly finished cooking, top it with the spring onion and rosemary mixture. Cook for an additional minute to allow the crust to adhere.

Remove the steak from heat and let it rest for 5 minutes to allow the juices to redistribute. Slice the steak against the grain, drizzle the garlic and Szechuan peppercorn butter over the slices, and garnish with fresh rosemary sprigs.