In a saucepan, large enough to hold sauce and pasta, heat olive oil over medium-low heat and gently saute garlic cloves 5 to 7 minutes, or until soft.
Add pieces of salt cod and raise heat slightly to cook cod on all sides, until it has lost its translucence. Scatter leek and parsley over fish and continue cooking until vegetables have become very soft, about 10 minutes. Add tomatoes, chile pepper, and salt and pepper, to taste, and stir to mix well. Cook, uncovered, for 10 minutes, to reduce and thicken tomato juices. Adjust seasoning.
Bring 6 quarts of water to a boil and add 2 tablespoons salt. Add pasta and cook until half done, about 7 minutes. Bring sauce back to a simmer, drain pasta and add to the sauce, stirring to mix well. Return to medium-low heat and cook, covered, until pasta is cooked through. Serve immediately, garnished with olives and parsley.