In a large skillet, over medium heat, saute the beef & onions until the onions are soft and the ground beef is cooked through- stirring occasionally. Drain the ground beef.
Return the meat mixture to the skillet and stir in the Worcestershire, and season with salt & pepper.
Spray a 9" pie pan with non-stick cooking spray. Spread the meat evenly into the pie plate. Sprinkle the cheese evenly out over the top.
Add the remaining ingredients to a medium-sized mixing bowl. Use a wire whisk to stir them together until evenly incorporated. Pour the batter out over the cheese-covered meat mixture.
Bake the pie at 400 degrees for 25 minutes, or until a butter knife inserted in the center comes out clean. Remove the cooked pie from the oven and let it rest for 2-3 minutes.
Top plated slices of pie with a drizzle of ketchup and yellow mustard, and garnish with a couple slices of dill pickle.