Light your grill to medium heat with two-zone cooking. We used our @biggreenegg XL set to 400º with @fogocharcoal .
We started by covering our @snakeriverfarms American Wagyu Sliders in our very own Red Tuxedo Rub (available from @spiceology). Add it to the indirect side of the grill and cook to 110º.
While the steak is cooking make some quick-caramelized onions. We did one whole onion with two tablespoons of butter, a dash of oil, salt, and honey. Cook on medium-high until slightly browned and soft (not crisp).
Make your blue cheese sauce with 1/2 cup mayo, 1/2 cup sour cream, 1/4 cup buttermilk, 4 ounces of blue cheese, a dash of Worcheshire sauce, salt, and pepper.
While the steak is cooking make some quick-caramelized onions. We did one whole onion with butter, oil, salt, and honey. Cook on medium-high until slightly browned and soft.
Once the steak hits 110º, pull it over to the direct side and get a good sear on each side. Pull the steak off at 125º internal and let it rest.
Toast your buns then top with the blue cheese sauce, sliced filet, caramelized onions, raw spinach, and some more blue cheese sauce.