1. Preheat oven broiler.
2. In a small bowl, beat egg yolks with a fork.
3. In another bowl, use electric beaters to beat egg whites and salt until soft peaks form.
4. Add beaten egg yolks and season with pepper, and then gently fold the mixture with a spatula.
5. Heat butter in a 22-25 cm (9-10 in.) non-stick, ovenproof skillet over medium-high heat.
6. Pour in egg mixture and spread out evenly in the skillet. Sprinkle with cheese and chives. Cook for 4-6 minutes, reducing heat after 2 minutes so the bottom of the omelette doesn't burn.
7. Finish cooking under the broiler; place skillet 10 cm (4 in.) from the element.

Note:
You can serve the omelette with a cherry tomato salad (dressed with oil, salt, and herbs), ham, or even potato and smoked salmon rostis.