Leek Tart

Preparation:

Preparation: Peel the leeks, remove the green leaves, cut the white part into 5 mm thick slices. Put them in a colander, rinse them and drain them. Melt 25 g of butter in a saucepan and brown the leeks for ten minutes. Add the broth, let it simmer for ten minutes. Drain them carefully. Add enough milk to the cooking broth to obtain 15 cl of liquid. Melt the remaining butter in a saucepan and add the flour. Cook for a minute, stirring constantly, until the flour is lightly browned. Wet little by little with the cooking broth from the leeks, beating with a whisk. Bring to the boil, then cook for two or three minutes, stirring. Put two egg yolks in a heatproof bowl, add the cream and mix. Gradually pour in the contents of the saucepan, beating with a whisk. Put the bowl in a bain-marie and let the sauce cook for ten minutes, stirring frequently but without bringing it to the boil. Preheat the oven to 170 degrees (thermostat 5). When the sauce is slightly thickened, remove it from the bain-marie and add 25 g of grated gruyere. Stir until cheese is melted; salt and pepper. Brush the bottom of the tart with the beaten egg and sprinkle with 25 g of grated gruyere. Arrange the leeks. Cover with the sauce and sprinkle with the rest of the grated gruyère. Place in the oven and cook for twenty-five or thirty minutes, until the tart is golden brown. Serve hot or warm.