(Preheat the oven to 200 degrees If making multiple omelets and store the cooked omelets on a baking sheet in the oven until all are finished)
Heat oil in a nonstick pan on low medium heat. Add the onion and cook until it becomes golden brown and soft.
Pour the eggs into the pan. As the eggs set around the edge of the pan, with a spatula, gently lift the egg to allow uncooked egg to flow underneath. When eggs are almost set on the surface but still look moist, add the cheese and chives. Slip the spatula under the omelet and fold over.
In the meantime, lightly toast the bread golden brown.
In a nonstick pan brown the chicken sausage on both sides.
Portion the omelet onto the bread, cut in half and serve with chicken sausage and sliced pears.