We will start by chopping an cooking the onion until they are glossy and shine.

To prepare the patties we need to mix the meat, panko, milk, eggs, cooked onions and some salt and pepper well.

To fill and form the patties I would suggest to use just a little bit of meat and make it as flat as possible in your hand. After placing the cheese on top, flip the corners inside of both the cheese and the meat and place another meat layer on top to close it up.
Don't make them to thick but try to close all gaps.

Cook the patties from both sides until golden brown and than pour some water and close the lid to let them steam for about 5 more minutes. 
Or until they are done.

While the patties are cooking you can prepare some sides. I made french fires but you can make anything you like.

After the meat is done place it on a separate plate and add ketchup and worchestershire sauce to the pan and heat it up again. You can add some herbs if you feel like the sauce would need some.

Now all that's left is to place everything on a plate and enjoy your meal!

Tip:

I got 8 patties out of those measurements. If you want to make less you could freeze up the remaining meat or divide it accordingly.