Salt and pepper the chuck roast on both sides. Heat the olive oil in a Dutch oven over high heat and sear each roast until deep golden brown. Remove roasts from pot and set aside on a plate.
Reduce heat to medium. Add garlic and cook until fragrant about 30 seconds, pour in beef stock, whisking to scrape the bottom of the pan. Pour in crushed tomatoes, pepperoncini's (with the juice) and the drained hot cherry peppers. Stir to combine, then put everything into the crock-pot including the roasts.
Cook for 4-6 hours on high or until meat is falling apart and adding the mushrooms for the last 30 minutes to an hour (enough so that they release there flavor and are softened but not cooked away).
Options: Should time allow, cool slightly then place the pot in the refrigerator for several hours to allow fat to harden at the surface. Use a spoon to scoop out the hardened fat (some residual fat is okay) then heat it up again on the stovetop. When the meat is heated again, remove the roasts to a cutting board. Use two forks to shred it into big chunks, then return the meat to the cooking liquid. Serve on toasted deli rolls or with rice, noodles or mashed potatoes.
Oven Method: Cook in a Dutch oven at 300 degrees for 4-6 hours.