Mince the onion and microwave in a heatproof bowl at 600W for 1 minute. Let it cool.

Combine breadcrumbs and milk in a bowl to moisten.

Mix ground beef and pork with salt and pepper in a separate bowl until sticky.

Add the cooled onion and moistened breadcrumbs to the meat mixture. Divide into 4 portions and shape into flat oval patties.

Place half the corn and butter in the center of two patties. Cover each with another patty and seal the edges to form stuffed patties.

Heat salad oil in a frying pan over medium heat. Cook the patties until browned on both sides.

Cover the pan and steam the patties on low heat for 7-8 minutes until cooked through. Remove from pan.

In the same pan, add the sauce ingredients (butter, ketchup, Worcestershire sauce) and simmer on low heat.