Heat tallow (or oil) in a Dutch oven; add the chopped onions and cook until they begin to brown. Remove the onions from the Dutch oven and set aside.
Combine seasoning salt, garlic powder, Italian seasoning, onion powder, and black pepper and rub over roast on all sides.
Sear the roast in the Dutch oven on all sides. About 2 minutes each side until browned.
Add in the carrots, potatoes and mushrooms.
Whisk together the broth, vinegar, tomato paste, Worcestershire sauce, honey, corn starch, paprika, salt and pepper, and pour over the roast and vegetables.
Two options for cooking:1. Put the lid on and roast at 275 degrees F for 3-3½ hours, or2. Cook covered, on low heat on the stove top for 2 - 2½ hours.Time will depend on the size of meat. Cook until meat is fork tender (easily pulled apart with forks) and vegetables are done. Note: if you want firmer vegetables, add them about half way through the cooking process. When done, remove the meat and vegetables from the Dutch oven and set aside.
On the stove top, over medium heat, slowly stir the whisked thickening agent (water and corn starch) into the gravy to thicken it.
Slice or shred the meat and serve with vegetables and gravy.