Ingredients Buckwheat spaghetti (“Fidelin del Moro”) or, them lacking, plain spaghetti – 250g White onion – a quarter Prosciutto crudo – ideally one 5mm-thick slice, alternatively 3 or 4 traditionally thin slices Extra virgin olive oil – two tablespoons Pecorino romano, grated – one tablespoon, heaped Parmigiano Reggiano, grated – one heaped tablespoon (two, if the Pecorino is…