The classic, creamy gratin is elevated into a dish par excellence in this langoustine gratin recipe. Langoustines, also known as Norway lobsters or scampi, look similar to miniature lobsters. They are known for their extraordinarily subtle flavor and texture, reminiscent of lobster. If langoustines are unavailable in your area, this gratin recipe can be prepared using shelled shrimp or lobster meat, as a substitute.
Cook's note: This recipe utilizes a broiler. Use only an enameled, cast-iron gratin pan or a pan that can withstand extremely high heat and rapid temperature changes. To avoid shattering and potential injury, do not use traditional glass casserole dishes for this recipe.
- 3 pounds langoustines, shelled after weighing
- 6 tablespoons butter, plus butter for dish
- 1 medium carrot, finely chopped
- 1 small onion, finely chopped
- 3 shallots, finely chopped
- 1 stalk celery, finely chopped
- 1 tablespoon fresh, chopped parsley
- 1/4 teaspoon dried thyme
- 1 small bay leaf
- 1/4 cup Cognac
- 1/2 cup dry white wine
- 3/4 teaspoon salt
- 1/8 teaspoon coarsely ground black pepper
- 2 pounds mushrooms, cleaned and thinly sliced
- 1 cup crème fraiche
- 3 egg yolks
- 1/4 cup water
- 1/2 cup grated Gruyere cheese
- 2 tablespoons fresh, finely chopped parsley
How to make langoustine gratin:
Butter a large, ovenproof, broiler-proof gratin dish and set it aside for a moment. Shell the langoustines, or shrimp if using, and twist off the tails. Reserve the tail meat for later. Place the shells and heads into a food processor and pulse them until they are coarsely chopped.
Transfer the pulverized shells to a large saucepan set over medium heat. Add 2 tablespoons butter to the pan and allow it to melt. Add the chopped carrots, onions, 1/3 of the shallots, and celery to the pan. Cook the vegetables and seafood shells for 5 minutes, stirring frequently. Pour half of the Cognac into the pan and carefully flambé it. Allow the flames to disappear. Pour the white wine into the pan, bring the mixture to a gentle simmer, reduce the heat to low, cover the pan, and cook it for 10 minutes.
Strain the liquid into a separate, clean saucepan. Discard the solids.
Using a third clean saucepan set over medium heat, melt 2 tablespoons butter. Add the remainder of the shallots and cook them, stirring constantly, until they soften, for about 4 minutes. Add the langoustine tail meat, seasoned with salt and ground black pepper, and cook the mixture, stirring constantly for 1 to 2 minutes, until the meat is just cooked through. Pour the remainder of the Cognac into the pan and carefully flambé it. Allow the flames to disappear. Strain the cooking liquid into the reserved cooking liquid from the shells. Set the langoustine meat and shallots aside for a moment.
Melt the remaining 2 tablespoons butter in the hot saucepan. Sauté the mushrooms, seasoned with salt and ground black pepper, stirring frequently, for 5 minutes. Strain the cooking liquid into the reserved cooking liquid. Layer the mushrooms onto the bottom of the butter gratin dish. Spoon the cooked langoustine tails and shallots onto the mushrooms. Set the gratin dish aside for a moment.
Whisk the crème fraiche into the reserved cooking liquid and bring the mixture to a simmer. Cook it down until it reduces by 1/3, leaving approximately 2/3 of the original volume. Transfer it to a large bowl to allow it to cool to room temperature rapidly.
Bring a small saucepan of water to a rolling boil. Combine 3 egg yolks with 1/4 cup of room temperature water in a heatproof bowl. Whisking the mixture constantly, set it over the water and gently cook it for a few minutes, until it becomes thick and the whisk leaves a clean trail through it. Stir it into the cream sauce.
Pour the sauce over the langoustines and mushrooms, sprinkle the surface with the Gruyere cheese, and then set the gratin dish under a broiler just until the top of the gratin turns light, golden brown. Garnish the gratin with the chopped parsley and serve hot.
This langoustine gratin recipe makes 4 to 6 servings.