Watching this with interest. When we go to Chicago, Portillos is always a stop, along with Rizza's on Clark Street a mile or so north of Wriggley Field.

Here is a recipe for Italian Beef.

Crock Pot Italian Beef

2-5 pound Chuck Roast, Rump Roast, Pot roast, Sirloin Roast (your choice – I use whatever is on sale)
4 cans Beef broth
1 teaspoon Pepper
1 teaspoon Oregano
1 teaspoon Onion Powder
1 teaspoon Lawry’s garlic seasoning
1 teaspoon Basil
1 package Good Seasonings Italian Dressing
1 or 2 large onions, sliced
1 or 2 jars peppercorn peppers (pepperocini) – seeded, or whole depending on desire
1 or 2 green peppers, sliced

Cook onions, peppers and pepperoncini in 1 can of beef broth for an hour at low heat until they are limp – these are used to dress the completed sandwich. I like to cook the veggies separately, but you can put them in the crockpot if you like, just not for longer than the last hour or two, else they fall apart and go to mush, which is bad.

Place beef in crockpot and add seasonings. Pour 3 cans beef broth over ingredients and cook at medium or low all day. When beef roast is falling apart, remove and shred (pull apart) with fork, returning meat to broth. I'm certain you can do this in the oven at 225 in a tightly covered roaster pan for overnight or all day.

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Nothing is Portillos though. When I was with Groen, we made a Capcold unit for them that they used to cook their Italian Beef roasts in their central commissary. They cooked it there and shipped to the locations. I never went to the central kitchen though and they had someone else do the installation of the cooker, which was essentially a several hundred-gallon square, SS crockpot with lots of controls to do overnight cooking of Cryovac packaged roasts with seasoning added to the cryovac bag.

They bought the seasonings preblended from someone and I was never able to find out who did the blend for them, or how much they used.

Some folks keep their secrets very secret.