I spent about an hour on Sunday making and cooking up a big batch of a basic burger mixture. The mix is very versatile, so I made four different things from it. Now I have enough mini-burgers, meatballs and more in my freezer for at least 20 or more bento portions. It was an hour well spent! I love just knowing that my freezer has a nice stock of ready-to-go bento items - it takes the pressure off considerably on busy mornings.
You can use more ground beef or ground veal or chicken instead of the tofu. The tofu makes it a bit lighter.
If necessary, make fresh breadcrumbs by chopping up 2 slices of bread (white or whole wheat) in a food processor. Moisten with a little milk.
Chop up the onion finely (I do this in the food processor too, after the breadcrumbs.) Saute in a little oil in a frying pan until soft.
Drain the tofu well and crumble.
Combine all the ingredients in a large bowl. Mix with your hands until a bit sticky and paste-like. The tofu should be all smooth and incorporated into the meat.
Heat up a frying pan with a little oil. Form the meat mixture into various shapes, as follows:
Mini-burgers: Take about 3 tablespoon-portions and form into little patties. Fry on one side, then turn and fry on the other with a lid on the pan for about 4 minutes until the patties are a bit puffed up.
Meatballs: Take 1 tablespoon-portions and form little balls. Roll around in the pan with a little oil until browned on all sides.
Stuffed tofu slices: Cut a slit into a small block of tofu, and stuff with about 1/2 Tbs. of the meat mixture. Dust the tofu with cornstarch and fry, turning all around, in a hot frying pan until browned on all sides.
Stuffed mushrooms: Twist off the stems of medium-size mushrooms, leaving the caps (use the stems for something else). Stuff each cap with about 1 Tbs. of the meat mixture, pressing down well. Put the stuffed mushrooms meat side down in a hot frying pan, and sprinkle the mushroom cap with a little salt. Turn over when the meat side has browned, lower the heat to low, put on a lid and let steam-cook for about 5-6 minutes.
Cool everything completely, and freeze. You can just put them in plastic freezer bags and take out only what you need.
Defrost either in a microwave for about 3-4 minutes, depending on how big your burgers or meatballs etc. are; or in a small frying pan with the lid on to steam-cook them. You can also pop them in a toast oven from frozen, wrapped in foil - they’ll take about 8-10 minutes this way.
The mini-burgers and so on will taste a bit bland when cold. To perk them up, you’ll want to add a sauce to them. The easiest are plain ketchup, oyster sauce, “Bulldog” sauce, or even soy sauce. Just heat up the sauce of your choice in a small frying pan and toss the defrosted mini-burger in it.
This little mini-burger is sauced with a mixture of 1 Tbs. ketchup, 1 tsp. Worcestershire sauce, and about 2 Tbs. red wine (per 3 of this mini-burgers). Add all the sauce ingredients to a small frying pan and mix; add the burgers to the hot pan, and coat with the sauce.
Teriyaki sauce  is also great, especially for the stuffed tofu slices. Sweet and sour sauce  works well too. The stuffed mushroom caps may not need any sauce at all - maybe a little drizzle of soy sauce on top if that.
You can also simmer the meatballs in a little homemade or store bought tomato sauce, crumble up the mini-burgers and stir fry with vegetables…and whatever else you can come up with.