Cut the mushrooms into thick slices, and on high heat saute in 2 tablespoons of butter in a non-stick frying pan on low heat.
In a medium bowl whisk the eggs by hand for 10 or 15 minutes until a frothy mousse forms on top. Add creme fraiche and chives. Season the eggs with sea salt and white peppercorns.
In a separate, large, non-stick frying pan melt 1 tablespoon of butter on a low heat, taking care not to burn it. Pour in the eggs and cook for about 2 minutes. The slower you cook it, the better the omelette.
When the omelette is cooked around the edges but still runny in the middle, add mushrooms. Cook until the eggs are firm, or to taste.
Using a spatula ease the omelette onto a plate and flip it in half. Slice into six portions.
Garnish with finely chopped chives and serve with a green salad.
*To crush peppercorns cover them with a cloth and crush with a rolling pin.