Bring 6 quarts water to boil and add 2 tablespoons salt.
Scale, gut and fillet sardines (you can also ask your fish monger to do this for you).
In a 12- to 14-inch saute pan, heat olive oil over medium high heat until just smoking. Add onion, currants, pine nuts, anchovies and red pepper and cook until softened, about 8 to 10 minutes. Add sardine fillets and fennel leaves and continue cooking 3 to 4 minutes, until fish pieces have just cooked, stirring carefully.
Cook pasta according to package instructions until just al dente and drain well. Toss hot pasta into pan with sardines and stir to coat. Add 1/4 cup toasted bread crumbs and parsley. Stir through and serve immediately. Sprinkle with remaining bread crumbs.