I used my 6 quart Instant Pot Duo 60 7 in 1*.

If you don’t want mashed potatoes then cook the roast for 70 minutes and then let the pot sit for 15 minutes before releasing any remaining pressure.

Slow cooker instructions: Pat the chuck roast with the salt and garlic powder. Pour broth into slow cooker and place the chuck roast into slow cooker. Cover and cook on low for 6 hours. Add in the potatoes and cook on low for another 2-4 hours (total time 8-10 hours). Use a slotted spoon to remove the potatoes. Dump the potatoes into a large bowl and mash. Add in the butter, milk, kosher salt, garlic powder and sour cream and stir/mash until creamy and smooth. Move the roast to a cutting board and let it rest. Use a fat separator to strain off the fat from the broth in the slow cooker. Add strained broth into a saucepan on the stove. Heat over medium high heat. Slowly whisk in the gravy packet. It will start to thicken in a couple of minutes. To make a thicker gravy add in a cornstarch slurry (in a small bowl stir together 1-2 Tbsp of cornstarch with 1-2 Tbsp of water, until smooth. Then pour the mixture into the saucepan. The cornstarch mixture will thicken up contents quickly). Salt and pepper the gravy to taste. Slice the roast or shred it up. Season it to taste with salt and pepper. Toast the slices of bread (optional). Place a portion of roast beef on a slice of bread on a plate. Top the sandwich with another piece of bread. Scoop some mashed potatoes on the plate. Ladle gravy over the top of the sandwich and mashed potatoes. Eat and enjoy!