Creamy Mushroom Potage with Fillo Cheese Gratin

Combine the finely chopped celery and beef broth in a large pot. Cook gently over low heat until the celery is completely soft and fragrant.

In a separate pan, toast the flour over low heat, stirring constantly, just until the raw flour aroma disappears. Keep it pale and do not let it brown.

Remove the flour from the heat and gradually whisk in the milk until smooth and lump-free. Stir this mixture into the celery and broth.

Add the chopped mushrooms to the pot and simmer gently over low heat until the mushrooms are tender and the flavors are well combined.

Melt the butter in a small saucepan and stir it into the soup to add richness and a silky finish.

In a bowl, whisk together the cream, egg yolk, and lemon juice. Temper this mixture by slowly whisking in a ladle of hot soup, then gently stir it back into the pot.

Season the soup with salt and black pepper to taste. Pour it into an oven-safe Pyrex or baking dish.

Sprinkle the surface evenly with breadcrumbs, then top generously with the grated fillo cheese.

Preheat the oven to 350°F (175°C). Bake on the middle rack for about 15 minutes, until the cheese is melted and lightly golden on top. Serve hot.