Make the coating batter ready:
Mix the egg, flour and water together. It should be thick enough so when you make a line through it with your chopsticks, it disappears slowly. If the batter is too watery it won't stick to the patties.
Finely chop the onions and put int oa bowl. Add all the ● ingredients except for the panko, and mix well until sticky.
Add the ● panko, and mix in well with your hands. If there aren't enough panko, add a little more.
Form into equal sized balls, and transfer to another plate. (we'll use the bowl to coat the meat in panko).
Put the panko into the emptied bowl.
Coat the formed meatballs evenly with the coating batter from Step 1. Use your left hand only for this.
Drop the patty into the bowl with the panko with your left hand, and cover with panko with your right.
When all the meatballs are in the bowl of panko, coat each completely and then flatten lightly to form patties. Don't press too hard or you'll make gaps in the coating.
We make them about this size. I flatten them just a bit more so that they cook faster.
Deep fry the coated patties in 180°C or so oil until golden brown on one side. Flip over, lower the temperature of the oil to about 160°C, and cook them through thoroughly. Raise the temperature back up to 180°C at the end for a crispy finish.
These patties cooked without a breadcrumb coating are hamburger steaks in our house. If there's any leftover coating batter, I make deep-fried sausages with it.
Story Behind this Recipe
I tried to recreate the menchi katsu my mother used to make when I was growing up, when I became an adult. ... I always thought that menchi katsu were things you made at home. But when I talked to other people, they told me that they thought it was something you buy at a store.
If you exchange the equivalent amount of cabbage for 1 of the onions, you'll have cabbage menchi katsu which are delicious too. When coating the patties in breadcrumbs, use one hand to dip them in the flour mixture, and the other to dip them in the breadcrumbs, to avoid getting the breadcrumbs all over your fingers. The menchi katsu are done when they make a sizzling sound if you squeeze them with your cooking chopsticks in the oil.