Preparation of fish stock: Shell the shrimp, keeping the tails aside and placing the heads and carapaces in a pot with 1 liter of water. Add one carrot, one onion, one celery stalk and boil for about 30 minutes. Strain and keep the broth hot.
In a separate pan, melt a knob of butter and quickly sear the langoustine tails with a pinch of salt and pepper (1-2 minutes per side is enough). Keep warm.
Cooking the risotto: In a frying pan, heat a little oil and sauté the finely chopped shallot. Add the rice and toast it for 2-3 minutes, stirring often. Deglaze with white wine and allow the alcohol to evaporate. Gradually add the fish stock, one ladleful at a time, stirring occasionally. After about 10 minutes, add the grated zest of half an orange and half a lemon.
When the rice is al dente, turn off the heat and stir in the cold butter. Add a drizzle of orange juice and mix well to blend the flavors.
Plating: Distribute the risotto on plates, lay the shrimp tails on top, and garnish with an aromatic herb (such as chives or fennel). Add a final grating of citrus zest and a drizzle of extra virgin olive oil.
