Add the ground beef, bread crumbs, egg, Worcestershire sauce, milk, garlic powder, onion powder, salt and pepper to a large bowl. Mix by hand until the ingredients are evenly distributed, but stop once the mixture looks even to avoid over mixing.
Press the meat down in the bowl to form an even disk-like shape. Use a knife to divide the hamburger mixture into 8 – 1/4 pound patties.
Line a baking sheet with parchment paper or foil. Using your hands, gather the burger mixture one at a time and press firmly into evenly shaped patties. Be sure to shape them just slightly larger than the buns you plan to use since they will shrink slightly during cooking.
Place the patties on the baking sheet. Use your thumb or the back of a spoon to press a dent in the centre of each patty so they don't puff up as they cook.
Preheat a gas or charcoal grill or a cast iron skillet to medium-high heat (approximately 350-400 degrees F). Brush with a little oil to prevent sticking.
Place the burgers on the oiled grill or in the skillet and spread about 1 1/2 teaspoons mustard on the uncooked side of each patty. Grill or fry the patties on the stove for 3-4 minutes per side, or until you achieve desired doneness.
Allow the burgers to rest for about 5 minutes. Place the hot patties on hamburgers buns, and top with desired toppings. Serve warm.