Tender, juicy hamburger calls for meat juices. Said juices must 1) exist 2) remain in the hamburger.
When you mix hamburger, you are breaking apart the muscle fibers in the meat and bringing out the juices. It is easier to break apart the fibers and bring out juices (myosin to us ubergeeks) if you are not trying to break apart onion or bread crumbs simultaneously.
Add bread crumbs or oatmeal, but only a small amount of milk, because you want the bread crumbs to absorb the juices and help keep them in the patty.
When cooking, do not turn more than once or twice. Turning over and over will cause the juices to work their way out of the patty. Brown each side on high heat, and then cook over low heat. The browned meat will act as a shell to seal in the juices.
I understand that in the USA and Europe, hamburger meat is entirely beef, and the fat content is influenced by the cut of beef used. In Japan, most ground meat is a 50/50 mix of beef and pork. (You can also get ground pork and ground chicken, and yes, ground beef, but most of the time what you will find in grocery stores doesn't contain enough fat to make a very good hamburger.)
I took yesterday and today off to get stuff done around the house and go shopping. To focus on my accomplishments:
1) I figured out what size coat I want to get this year from Uniqlo. I'm thinking a very youthful pale pink or a practical but trendy glossy beige would be nice this year, both which are only available online, but I wanted to be sure of the size.
2) I bought supplies to sew the Pumpkin Princess a makeshift tutu. She's into princesses and twirly skirts, but it's a bit cold to let her wear stuff like that to day care these days. I thought if I could make some kind of lightweight skirt, she would wear it over her pants or leggings. I made a short, fat, tube of fabric, hemmed one side, rolled down the other to make an elastic waist, and stiched on a layer of tulle. I expect the Pumpkin Granny will stitch on the second layer of tulle and thread elastic through the waist sometime within the next week, which would be nice. I promise pictures if this happens.
3) I made buri daikon, a lovely dish of root crops and fish last night.
4) I made cream of carrot soup and hamburger steaks tonight.
So that's some stuff done, but not as much as I would have liked. Which I kind of expected to happen. Oh well.