Preheat oven to 350 degrees. Spray a 9x13" baking pan with non-stick cooking spray and set aside.
In a large mixing bowl, add ground beef, crushed crackers, milk, Worcestershire sauce, and all seasonings.
Using your hands or a wooden spoon, gently mix all ingredients together.
Form into 8 patties (remember that they shrink when they cook!).
Place 3/4 cup flour on a plate or in a bowl. Dredge all of the patties in the flour.
Place a large skillet over medium-high heat. Melt 3 Tablespoons butter in the skillet. Once hot, add patties to the skillet (you probably won't be able to fit all the patties, so work in batches).
Sear both sides of the patty until it turns golden brown, about 1-2 minutes per side (don't worry about cooking it all the way through - it will finish cooking in the oven).
Place the patties in the prepared baking pan.
To make the gravy, use the skillet that you browned the patties in. If needed, add in 1 Tablespoon butter. Turn the heat to medium and add the onions and mushrooms, scraping up the browned bits in the pan from the patties while sauteing the vegetables. After the onions start to turn soft (after 3-4 minutes), add in the garlic and cook for 1 minute more. Remove pan from heat and add in cream of mushroom soup, milk, and Worcestershire sauce. Stir well, then pour the gravy evenly over the top of the patties in the pan.
Cover the dish with aluminum foil.
Bake for 30-40 minutes or until meat is completely cooked.
Serve topped with fresh parsley, mashed potatoes on the side, and roasted broccoli or green beans for a complete and easy meal!