Gently combine the pepper to the cheese. Stir until thoroughly combined. Store in the fridge until ready to use. (Feel free to increase the amount of pepper used depending upon your love of this spice.) Set aside.
Pat steaks dry with paper towels and even season all sides of the steak with the salt.
In a cast iron skillet, heat 1 tablespoon of oil over medium-high heat until just smoking, about 4 minutes. Lay steaks in the skillet and cook until well browned on first side, 3 to 5 minutes.
Flip the steaks and reduce the heat to medium. Cook until the internal temperature of the steak reaches 120 to 125 degrees (for medium rare), 5 to 7 minutes. Remove the steaks from the skillet and place onto a rimmed cutting board, cover with aluminum foil and let rest.
Add the onions to the skillet and let cook for 3 minutes, stirring often to pick up any browned pieces stuck to the skillet. Add the brussels sprouts and stir to combine. If the pan looks dry, add an additional 1 tablespoon of olive oil. Cover and cook for 5-8 minutes, or until the brussels are cooked to preferred texture. Stir occasionally.
Remove the skillet from the heat. Stir in the arugula, vinegar and 3 tablespoons of the Peppered Goat Cheese. Slice the steak. Serve the steak and brussels topped with goat cheese to taste.
