Ingredients :

• Eggs — The absolute base. Get them at room temperature if you can — they whisk better and provide more volume. Use free-range eggs if you can find them: the yolk is more orange and the texture richer once cooked.
• Baking powder — This is the secret behind the puffed texture. One teaspoon is enough — no need for more, otherwise it leaves a slightly bitter aftertaste. Check that it hasn’t expired: stale baking powder won’t lift a thing.
• Flour — One and a half tablespoons, no more. Its role is to stabilize the preparation and prevent the omelet from collapsing too quickly once out of the oven. Always mix it with the baking powder in a separate bowl before incorporating — otherwise you risk lumps.
• Grated cheese — Optional according to the recipe, but hard to skip once you’ve tried it. Emmental or Gruyère work well — they melt without releasing water. Avoid pre-shredded bags: they often contain anti-caking agents that prevent proper melting.