Whisk the eggs in a bowl and add a pinch of salt just before you are ready to cook. Melt the butter with a drop of olive oil in a pan over medium heat, then turn the heat down to low. Pour in the eggs and let them sit. When one side can be lifted with a spatula, fold about a third of the omelette over onto itself. Wait until the other side can be lifted and fold it over, or keep folding from the same side as it cooks. Watch closely and don't overcook it. Serve with grated parmesan, salt and pepper.