This original recipe is from one of Harumi Kurihara's. I just adjusted the ingredients a little by replacing half of the onion with leeks.
Also, if you don't like pork, you can always make an all beef version or even an all chicken version *_^
1. In a small bowl, combine breadcrumbs and milk. Set aside.
2. Sweat the onion and leek until they are just soft, do it on low heat so you don't burn them (if you like stronger onion taste, skip this step). Set aside and let cool before adding to mince.
3. In a bowl, combine beef and pork mince, soaked breadcrumb, cooled onion/leek, egg and season with S&P.
4. Take a small handful of the mixture, and shape into an oval shape, and throw it from one palm to the another ( this is probably no the correct wording, but hopefully you get the idea. Or, go play Cooking Mama on Nintendo DS :D)
5. There are 2 ways to cook the hamburger : - Frying Pan Method : turn the heat to medium, put the meat on the pan and cover. The trapped steam will help to cook the meat all the way through. Flip the hamburger to brown the other side when the meat starts to turn greyish - Oven Method : Preheat oven to 230 C , in a dish that can handle the oven heat , brown the meat on both side, and pop into the oven for another 15 minutes.
Teriyaki Sauce :
Combine everything and simmer until the sauce starts to thicken.