Add saffron threads to a glass, then fill it with hot water and let it rest. For the best results, do this the day before.
Take a medium-sized pot and boil the wild fennel leaves. Then, after about 5 minutes, strain the leaves and transfer them to a small plate before chopping them into small pieces. Save the water to use later.
Add the pine nuts to a small pan and toast them on medium-low heat, until golden, then set them aside.
Heat a large pan before adding 2 tablespoons of EVOO. Then toast 5 tablespoons of breadcrumbs, stirring with a wooden spoon so they cook evenly. Once ready, set aside.
Place the frying pan back on medium-low heat and add 4-5 tablespoons of EVOO and the red onion.
Before the oil gets too hot, add a splash of water and the crushed garlic, then stir.
Add the anchovies, stirring well until they melt and disappear.
Incorporate the tomato paste, stirring to combine and add color to the dish. Add a splash of water if it dries out too quickly and slightly lower the heat if needed.
Add the chopped fennel leaves and sultanas, mixing well.
Pour in half of the saffron mixture, then gently add the sardines and cook for less than 2 minutes, stirring carefully.
Season with a small amount of salt (only if needed) and a generous crack of pepper.
When the liquid evaporates, add the rest of the saffron liquid.
Using the water from the fennel leaves, bring it to a boil (adding more water if needed and moving it to a large pot), add 1 tablespoon of rock salt and allow to dissolve. Cook your pasta according to the time noted on your pasta packet.
Scoop up a mug full of pasta water and set it aside once the pasta is almost cooked.
Strain the pasta and add it to the pan with the sardines.
Add the toasted pine nuts, toss the pasta, and add some of the reserved pasta water as needed to ensure the pasta is well coated with the luscious sauce.