Clean the prawns, removing the shell and the intestine. Set aside the heads and shells for the stock. Rinse and dry the prawns.
Cut the prawns into pieces and toss them with extra virgin olive oil, lime juice, and lime zest.
In a pot, combine the prawn heads and shells with around 1 liter of cold water. Bring to a boil and simmer for about 30 minutes. Strain the broth and keep it hot.
PREPARING THE RISOTTO
In a large pan, sauté the minced onion with some oil and a few coarse salt flakes until transparent. Add the rice and toast for a few minutes.
Deglaze with white wine and allow it to evaporate. Gradually add hot fish broth, stirring often.
Halfway through cooking, add the saffron dissolved in some hot broth. Continue cooking, adding broth as needed.
When the rice is al dente, remove from heat and stir in butter and Parmigiano cheese. Let the risotto rest for a minute.
SERVING THE DISH
Serve the risotto by placing a few prawns on the surface. Garnish with thyme, toasted hazelnuts, and a few drops of Giusti Reserve 100.