-2 lb Sirloin Slab (I couldn’t find this exactly, so I bought 2 separate sirloin steaks, that equaled about 2lbs.)
-Montreal Seasoning, applied liberally (I bought a huge container of this at BJ’s. We use it for grilling too.)
-Packet of Au Jus (made according to the directions)
-Mayo and Horseradish (Mixed)
Apply Montreal Seasoning to sirloin. Cut onions in slices. (I didn’t separate these, just left them in chunks.) Place them all over the sirloin. Place the sirloin in a covered roaster with a short drain rack on the bottom and slow cook the sirloin slab. Cook on low, using a thermometer. (I put my oven a little under 200 and cooked it for 4 hours.) You don’t want to go above 170 degrees. (When I pulled ours out, the temperature of the meat was 150.) This is best done cooked the day before. Refrigerate sirloin and juices. The following day, shave your sirloin into slices. (This was done with a slicer when we had it. It was recommended to be done with an electric knife if no slicer was available. I didn’t have either, so I slowly, painstakingly sliced the sirloin as thin and uniform as I could get it with a very sharp knife.) Pour the juice in a serving pan and line the pan with the slices. (I didn’t have a lot of juice from mine, so I went ahead and prepped the Au Jus and added a bit to the pan to coat the sirloin. I wanted it all covered so that it didn’t dry out.) Place in the oven to get warm. (I heated mine on 350 for about 10 minutes.) Turn to warm for 45 minutes to an hour to allow the meat to marinade.
Lightly butter your rolls and toast on a skillet. Mix together the mayo and horseradish, spread onto the bun. Place the amount of sirloin you want for one sandwich on the griddle, cover with cheese and allow to melt. (We also used onions on ours.) Serve with Au Jus to dip.