Reserve ¼ of the pepperoncini peppers, scallions, a tablespoon brine, a few garlic cloves, 2 tablespoons butter and a couple tablespoons of diced onion to make the pan sauce later.
Place roast in the Instant Pot (or slow cooker or dutch oven) and pour remaining ingredients over roast. For a bit of extra flavor, use the sear function to brown meat before adding seasoning.
3-4 pound boneless beef chuck roast, 1 cup pickled pepperoncini peppers and brine, 2 cups beef broth, ¼ cup butter, 3 tablespoons Worcestershire sauce, 1 large onion, 1 head garlic, ½ teaspoon black pepper, 2 tablespoons dried parsley, ½ teaspoon dried dill, ¼ teaspoon dried thyme, ¼ teaspoon dried basil, ¼ teaspoon dried rosemary, ¼ teaspoon dried oregano
Secure lid to seal and set the electronic pressure cooker on high for 90 minutes. Allow to depressurize naturally at least 15 minutes, then release any remaining steam and remove the lid.
Remove meat and set aside in a large bowl to be shredded. Pour juices into a jar or tall container to separate the fat from the broth.
Shred beef with two forks and return to cooking vessel to keep warm.
Once juices have separated remove the rendered fat, saving 1 tablespoon and discarding the rest. Add 1 tablespoon rendered fat with remaining 2 tablespoons butter to skillet over medium heat. Add scallion whites, and reserved garlic and the diced onion. Cook until fragrant, about a two minutes, then whisk in flour and continue cooking for about a minute longer. Pour in reserved pepperoncini juice and slowly add just enough of the pan juices as needed to thicken, usually about 3 cups. Simmer to test thickness, add additional juices as necessary to thin.
3 tablespoons all purpose flour, 3 medium scallions
Toss shredded beef with ¼ cup pan sauce. Garnish with scallion greens and pepperoncini peppers and serve with remaining sauce on the side.