Omelette

Separate the egg whites, in a large bowl, and yolks in another smaller one

If eggs are frozen, let them thaw for an hour

Then beat the egg whites until frothy with tartar cream

Important detail: when lifting the whisk, the mixture should form firm peaks like in the photo

Next, beat the yolks until white, with salt, mustard, pepper, and gradually add milk

Using a manual whisk, mix the yolks into the egg whites beaten to froth, making rotational movements from top to bottom

Let everything be smooth, but don't overbeat

Slowly warm a 25cm diameter frying pan and add oil and butter

Let it melt, spreading the fat on the sides, greasing them

Pour in the egg mixture evenly, using a 'hard-to-scratch' (spatula for scraping bowls)

The frying pan handle should not be flammable

Cook over low heat, without stirring, for about 2 minutes

Then put the frying pan in the oven (preheated) for 15 minutes or until the egg mixture is golden and the top part is firm when lightly touched with the finger

While the omelette cooks, prepare the cheese sauce

In a small pan, melt butter

Remove from heat and add: wheat flour, mustard, salt, pepper, and milk

Mix well and put back on heat

After bringing to a boil, mix until thickened

Lower heat, add grated cheese, and cook, stirring, until the mixture is smooth

Make a cut of 1 cm depth just off center of the omelette

Fold the smaller part over the larger one and release with a spatula, pushing slowly into a plate

Pour the sauce over the omelette and finish with chives

Serve about 4 portions.