Toast the shells in a small saucepan with a little olive oil, then add about 2 cups (500 grams) of cold water. Bring to a boil and let simmer over medium heat for at least 10 minutes to make a flavorful broth. Turn off the heat and let cool slightly, then season with salt and add the oregano.

In the same hot skillet, add the pasta and cook it as you would risotto, gradually adding the broth made from the shells and, if needed, extra water. This way, the starch released from the pasta stays in the pan and helps create a creamy sauce with the fish broth. Continue until the pasta is cooked al dente; it may take a few minutes longer than the package instructions (taste to check!).

Plate the pasta and garnish with a pinch of oregano, a grind of pepper, and a sprinkle of red pepper flakes.