Preheat the oven to 300°F.
Rinse and pat dry the chuck roast. Season with salt and pepper on all sides.
Heat a large skillet with oil on medium high heat until oil is hot. Add the chuck roast to the skillet and sear for 4-5 minutes. Flip and repeat until both sides are golden brown.
Add the seared roast to a large casserole dish or Dutch oven.
In the same skillet, add onions and minced garlic and sauté for 2-3 minutes. Pour in the broth and bring to a simmer.
Pour the broth and onions into the dish around and under the roast.
Sprinkle the gravy mix and ranch powder over the beef. Top with pepperoncini’s, pepperoncini juice, and cubed butter over the roast and cover the dish with foil or lid.
Roast at 300°F for about 3-4 hours, until the roast is tender and falls apart easily. (The time will depend on the size of the chuck roast, typically you want to bake 1 hour for every pound.)
Once the beef is tender, remove from the oven and carefully shred the beef with two forks. (If you want to make some gravy from the juices, remove about 3/4 cup of the liquid before shredding the beef.)
Top with freshly chopped greens and serve immediately with desired sides.