How to Make It
Place baccalà in a large bowl; add cold water to cover, and let soak in refrigerator 48 hours, changing cold water twice a day. Drain baccalà, and cut into 6 pieces (about 3 ounces each). Set aside.
Bring 6 cups water and 21/2 teaspoons salt to a boil in a medium saucepan over medium-high. Gradually add polenta, whisking constantly. Return mixture to a boil, whisking constantly. Reduce heat to medium-low, and cook, uncovered, whisking occasionally, until polenta is tender and creamy, 45 minutes to 1 hour. Remove from heat, and whisk in mascarpone until smooth. Cover to keep warm until ready to serve.
Heat 2 tablespoons olive oil in a large skillet over medium. Add onion, garlic, and red pepper, and cook, stirring occasionally, until softened and onion is translucent, about 6 minutes. Add wine, and cook, stirring occasionally, until mostly evaporated, 8 to 10 minutes. Add crushed tomatoes and their juices, olives, oregano, black pepper, bay leaves, and remaining 1/4 cup olive oil. Cook, stirring often, until sauce is slightly thickened, about 8 minutes.
Add cod to tomato sauce, and simmer, stirring occasionally, until cod flakes easily when pressed with a fork, 16 to 20 minutes, flipping cod pieces after 10 minutes. Stir in remaining 1/2 teaspoon salt or more to taste. Remove and discard bay leaves. Serve cod and sauce over polenta. Sprinkle with parsley, and serve with lemon wedges.