Step 1

Season each side of the chuck roast with 1 teaspoon seasoning salt.

Step 2

Set slow cooker on Low and spread out onion slices in a single layer on the bottom of the pot. Reserve a few slices for the top of the roast.

Step 3

Heat cooking oil in a nonstick skillet over medium-high heat until the oil shimmers. Brown seasoned roast in the hot oil, 3 to 4 minutes per side. Place on top of the onion slices, and pour undiluted consomme and Worcestershire sauce over the top. Cover with reserved onion slices.

Step 4

Cover and cook on Low until the beef is very tender, 8 to 10 hours.

Step 5

Remove beef from the slow cooker and place on a cutting board. Using two forks, shred the meat and discard fat and membranes. Return shredded meat to the slow cooker and keep warm.

Step 6

Melt butter in a nonstick skillet over medium heat. Open buns and place in the skillet, cut sides down. Toast for 2 to 3 minutes. Repeat for remaining buns, adding additional butter, if desired.

Step 7

Place a piece of cheese on each bun half. Add 1/3 cup shredded beef, squeezing out most of the liquid, and cooked onions, as desired. Cover with the top buns. Serve warm.