Make the beef filling. Heat a large pot over medium-high heat. Season the beef sirloin with salt and pepper and then coat with the flour. Add the butter and oil to the hot pan. Once the butter has melted, brown the meat on all sides. Remove the beef with a slotted spoon, and set aside. Deglaze the pan with the wine, scraping up the brown bits from the bottom. Bring the wine to a boil and cook for 1 minute. Pour in the beef broth and Worcestershire sauce. Add the browned beef, potatoes, carrots, peas, and corn to the pot. Season with parsley, sugar, garlic powder, onion salt, pepper and bay leaf. Bring the mixture to a boil. Turn the heat down to low. Cover and cook for 20 minutes, or until the beef is cooked through and the vegetables are soft. Remove the bay leaf. Stir in the mixture of 2 tbsp of flour + 2 tbsp water.
Assemble the pie. Lightly grease the bottom and sides of a pie plate. Press one of the pie crusts in the bottom of the pie plate. Carefully pour the beef mixture into the pie crust. Cover with the second pie crust. Make slits in the top of the pie crust.
Bake in a preheated oven according to pie crust baking instructions, or until the pie crust is golden brown. Cover the edges of the pie crust about 15 to 20 minutes after baking, so they don't burn.
There's no need to allow the pie to sit - you can slice it immediately. Be careful - it's hot! My husband likes to drizzle a little brown gravy on top of his.