1. In a saucepan, blanch the asparagus in boiling water, 3 minutes. Drain and let cool in cold water. Set aside.

2. In a skillet, heat the oil. Add the onions and cook for 3 minutes. Set aside.

3. In a large bowl, whisk the eggs into an omelette. When they are well whipped, season with salt, pepper, and parsley.

4. In a non-stick pan, melt the butter. Pour the beaten eggs and cook the omelette over medium heat, bringing the eggs from the edges towards the center so that the mixture cooks evenly.

5. Sprinkle the roasted onions over the surface of the omelette. Place the asparagus and fold the omelette. Serve immediately.