Prepare the cowboy butter: In a medium bowl, combine softened butter, minced garlic, chopped parsley, chives, Dijon mustard, lemon juice, smoked paprika, and cayenne. Mix thoroughly until well incorporated. Set aside at room temperature.
Season the steak: Pat steak cubes dry with paper towels. Season generously with salt and pepper on all sides.
Heat the pan: Heat olive oil in a large cast iron or stainless steel skillet over high heat until shimmering and just starting to smoke.
Sear the steak bites: Add steak in a single layer (work in batches if needed). Sear undisturbed for 2 minutes until golden crust forms. Flip and cook 1-2 minutes more for medium-rare.
Rest the steak: Transfer steak bites to a plate and let rest for 3-5 minutes.
Coat with butter: Return skillet to medium heat. Add half the cowboy butter. Once melted and fragrant, toss steak bites back in, coating thoroughly.
Serve immediately: Plate the steak bites and serve with remaining cowboy butter on the side for extra drizzling.