Mince the onion and fry in oil. Remove from heat and set aside until the heat dissipates.
In a bowl, mix the panko, milk, egg, ground meat, onion (from Step 1), salt, pepper, nutmeg, and garlic powder.
Mix until incorporated and sticky (at this point, it should be loose and with a whitish color).
Divide the mixture, punch out the air pockets, and form into a patty.
Pour a thin layer of oil in an unheated pan and add the patty. It's quite soft, so fix the shape.
From the center of the patty, spread out to a 2 cm thick oval shape. Avoid letting the patty crack. Turn the heat on to medium and cook.
Gently shake the patty in the pan and once it's cooked on one side, slide onto a plate (it's still soft so be careful).
Remove the excess oil from the pan and slide the uncooked patty onto the pan. Cover and cook on low heat for 5 minutes.
Add a pat of butter, Japanese Worcestershire-style sauc,e and ketchup to the oil in the pan and heat.
Pour the sauce on the patty and it's done.
Story Behind this Recipe
It's said that it's hard to know when hamburgers are cooked through, so I cooked these thin and spread out so it's easy to tell.
Add the onions once they have cooled down. When cooking, don't poke a hole or cut the patties. The juices will seep out of the patties. If you're worried that the heat didn't cook through, microwave for 30 seconds. If you like, use your favorite sauce.