White omelet with greens

For ➊
2 egg whites
1 knob of butter
salt & freshly grounded black pepper
a handful of mesclun (or mixed greens, from bitter to sweet)
walnut oil

Beat 2 egg whites with a pinch of salt. Melt butter in a frying pan. Add the egg whites. When done, but not stiff, sprinkle with salt and pepper. Put a handful of greens on one half, drizzle with walnut oil and fold the omelet.