1. Hard boil the eggs and plunge them in cold water
2. Cut the mushrooms and sauté them in olive oil, season with salt, pepper, add garlic and parsley
3. Prepare the béchamel sauce
4. When the mushrooms are golden brown, set them aside and in your skillet (if it is oven-safe) or a baking dish, spread a little béchamel sauce
5. Blend the mushrooms, you can leave some pieces for texture
6. Peel the eggs, cut them in half, and mix the yolks with the mushrooms, a generous spoonful of béchamel sauce, and stir
7. Place the cooked egg whites in your skillet on the bed of béchamel sauce and stuff them with the mushroom and egg mixture
8. Cover with béchamel sauce, sprinkle with gruyère cheese and breadcrumbs seasoned with parsley and garlic
9. Bake in the oven to gratinate