They really don't take a lot of thought to stick together, and its more a matter of assembly and construction than it is measuring and mixing.
Its helps if you have your own hens, and a ridiculous amount of good, free-range eggs that need using up, but thats just me.
Beat the eggs and add some milk to dilute. If you have some cream, chuck that in too. This pie dish was about 8 inches across, and I used half a dozen eggs.
Construct - layer the onions, ham and pepper (or whatever fillings you are using) in the pie dish and cover with the eggy mixture. Top with cheese and a few twists of black pepper, and perhaps some herbs of your choice.
Bake in a medium oven until it is done. Its done when the egg has "set" - you can test by lightly shaking the pie dish - if the egg looks runny then it isnt quite finished.
It should last around three days.