1. In a bowl, whisk together butter, horseradish, mustard, honey, lemon zest, and chives until uniform. Season to taste with salt and pepper.
2. Using a spatula, scrape out mixture onto plastic wrap, forming into a log. Refrigerate until firm.
3. To make the rub: In a dry pan, toast all sesame seeds, poppy seeds, peppercorns, and mustard seeds for about 3-4 minutes or until fragrant. Place in small food processor along with salt, brown sugar, onion, and granulated garlic. Pulse until finely ground.
4. Preheat George Foreman® Smokeless Grill Series to Medium-High.
5. Brush steaks with vegetable oil and coat in a good amount of the black powder rub. Place on grill and do not move for 5 minutes, turn 90 degrees to form a grill mark “cross hatch” and cook for another 5 minutes. Flip and repeat until desired temperature is reached. For medium, cook to an internal temperature of 140°F, for medium rare, 130-135°F.
6. Let rest for 5 minutes. Using a sharp knife, slice into 1/2-inch thick pieces. Arrange slices on a plate and top with a couple 1/2-inch disks of the horseradish butter. Top with crispy onions and fresh parsley.