Place the squash on a cutting board, and work very carefully. First slice off the stem end of the squash, then stand the squash upright on the flat end and carefully slice it in half from the top down to the cutting board.
In a large bowl, combine ground beef, breadcrumbs, milk, egg yolk, soy sauce, Worcestershire, garlic powder, onion powder, and pepper. Gently mix until thoroughly combined but not packed down.
Divide the beef mixture into 8 equal portions and gently roll into balls which should measure between
1-1/2 and 2 inches across.
Arrange meatballs on prepared baking sheet, at least an inch apart.
In a saucepan set over medium heat, prepare sauce by combining pineapple, green pepper, water, soy sauce, honey, rice wine vinegar, brown sugar, and ginger.
whisk together cornstarch and water.
Stream cornstarch mixture into simmering sauce while stirring. Allow sauce to cook for a few minutes until thickened.