Trim fat from meat; save big pieces to render out for drippings.
Using a very sharp knife, cut meat across grain in slices 1/8 to 1/16 inch thick.
Cut white onions into eighths; slice green onions lengthwise, then cut crosswise in 1 1/2 -inch strips; seed green peppers and cut in small strips with slanted sides; slice celery diagonally in 1/2 inch-wide strips; slice the mushrooms lengthwise (stems, too) in pieces 1/8 inch thick; wash spinach, remove stems, and cut large leaves in half.
Mix together in a pitcher soy, bouillon cube which has been dissolved in the 1/2 cup water, monosodium glutamate, sugar, and salt.
To start the first batch of sukiyaki, render out meat fat in a heavy pan under high heat; remove cracklings.
Add one-half of the meat; cook and stir until meat is brown.
Add half the white onions, green pepper, and celery, and stir lightly; add half the soy mixture, and stirring often, cook rapidly for 5 minutes.
Stir in half the green onions and mushrooms, and cook for 1 minute.
Mix in half the spinach and cook 1 minute.
Because sukiyaki cooks quickly, wait until your guests are halfway through the first batch before starting the second.
This recipe will serve 4 persons with plenty for second helpings.
Sukiyaki has such flexible proportions that it is easy to double or triple the ingredients for a crowd.