Chop up the onion. Sauté the ground beef in a fryng pan, and when some fat comes out of the meat add the onion and sauté it together.
Season with salt, pepper and nutmeg, and saute until cooked. This is the filling for the omelette. It cam be kept in refrigerator for 2 to 3 days.
Make the omelette: Break the eggs into a bowl and beat well. Heat some oil in a frying pan and pour in the egg.
Put the filling on one half of the omelette, and fold over the other half.
Form the omelette as it cooks, to your desired doneness.
Another way to make the omelette:
Break the eggs into a bowl, add the filling, and mix well.
Heat some oil in a frying pan, pour in the egg mixture and cook to your desired degree of doneness.
Decorate with ketchup with love.
To make an omelette for bento use:
Mix 1 egg with 1 to 2 tablespoons of the filling. Make a tamagoyaki (rolled omelette) using a small square tamagoyaki pan.
When making an omelette for bentos, make sure to cook it thoroughly.
Story Behind this Recipe
I've adapted an omelette my mother used to make for me to suit modern tastes. My mother used to make a usuyaki tamago (very thin omelette) and wrap ground meat and onion in it.
I recommend using lean ground meat. I usually use Australian lean ground beef. If you stock some extra sautéed ground meat and onion you can make this omelette any time, so I've given amounts for making 1 omelette and for stocking some.