Steps
- Peel 225g of small raw shrimp, reserving the shells. Cut the shrimp into ¼in / 5mm pieces.
- Melt 1 tablespoon of unsalted butter in a saucepan over medium heat. Cook 1 small sliced onion for 2-3 minutes. Add the shells and cook for 2 minutes.
- Add 1¾ cups of milk and ½ bay leaf. Bring to a boil, then simmer uncovered for 15 minutes. Strain, discard the solids, and return the milk to the pan.
- Poach the shrimp in the milk for 3 minutes, then strain and reserve both. Sprinkle 7g of powdered gelatin over 5 tablespoons of cold water.
- Melt 4 tablespoons of unsalted butter over low heat. Stir in ⅔ cup of all-purpose flour, then gradually whisk in the reserved milk. Simmer for about 7 minutes, until thick and smooth.
- Stir in 55g of grated Gruyère until melted. Gently warm the gelatin mixture for 1-2 minutes, until dissolved, then stir it into the sauce. Remove from the heat and cool briefly.
- Beat 1 large egg yolk with 5 tablespoons of milk. Stir into the sauce with the shrimp, 1 tablespoon of lemon juice, and 1 pinch of cayenne. Season with salt, pepper, and nutmeg.
- Spread in a plastic-wrap-lined 9in / 23cm square pan, cover the surface, and refrigerate overnight. Unmold, cut into 3 × 1½in / 7.5 × 4cm rectangles, and roll each into a cylinder.
- Beat 3 egg whites with ½ teaspoon of salt and 1 tablespoon of vegetable oil until frothy. Coat the croquettes in ½ cup of all-purpose flour, the egg mixture, then 1 cup of dried breadcrumbs.
- Heat 2in / 5cm of vegetable oil to 375°F / 190°C in a deep saucepan. Fry in small batches for about 3 minutes, until deep golden and hot inside. Drain on paper towels.