Preheat oven to 300 degrees.
Pat the venison roast with paper towels to dry it and liberally salt all sides with 2 teaspoons of kosher salt.
Set your large Dutch oven on the stovetop over medium high heat and add cooking oil. Once the oil is shimmering add the venison roast and sear on all sides.
Remove the seared venison and set aside, then reduce the heat to medium.
Add chopped onion and mushrooms to the pot, along with another drizzle of cooking oil if needed. Saute until onions are tender, then add minced garlic and cook for an additional two minutes.
Stir in flour and tomato paste, along with beef stock, A.1. steak sauce, soy sauce, Worcestershire sauce, brown sugar, and black pepper. Scrape the bottom of the pot to loosen any burnt on bits.
Add venison back into your Dutch oven and cover with the lid. Place in your oven for 3 hours.
After three hours remove the lid of your Dutch oven, add a sprig of sage, bay leaf, and two tablespoons of butter, then let the meat braise for an additional hour.
Remove the pot roast from the oven, discard bay leaf and the sprig of sage. Shred the meat if desired, or slice the venison roast across the grain into slices and serve with mushrooms and the braising liquid as gravy over mashed potatoes.