Preheat oven to 350 degrees F (175 degrees C). Grease a 9x9 inch baking dish and set aside.
Form ground beef into 20 meatballs. Brown them on all sides in a large skillet over medium heat, about 15 minutes.
Whisk together the ketchup, cornstarch, water, sugar, vinegar, dry mustard, salt, and soy sauce in a bowl until the sugar is dissolved and the cornstarch is smooth.
Place the browned meatballs in the prepared baking dish, and pour the sauce over them. Bake 30 to 40 minutes in the preheated oven, until the sauce is thickened and the meatballs are cooked through.
