Once the meat and vegetables are cooked and set aside, prepare the egg mixture. It works best to mix together enough for just 1 skillet at a time.
In a bowl, beat together the eggs, milk, and a dash each of salt and pepper.
Grease then heat a 10" cast iron skillet over high heat.
When the skillet is hot, pour in the egg mixture and rotate the pan in a circular motion until the egg evenly coats the bottom of the pan.
As the egg cooks, gently push the cooked part toward the middle of the pan and allow the uncooked part to run to the outer edges. *Don't break up the eggs though.*
When the eggs are nearly completely cooked, sprinkle the meat/vegetable toppings on half of the omelette then sprinkle the cheese on top of the meat and vegetables.
Flip the empty side of the eggs over the toppings and finish cooking.
When the omelette is completely cooked, carefully slide the omelette onto a platter, sprinkle some cheese over the top, and keep warm in the oven.