Heat 2 tablespoons olive oil in a medium saucepan over medium heat. Add shallots and cook until soft. Add wine and cook until almost reduced. Add saffron and stock and bring to a boil. Add the beans, chickpeas, sausage, and mussels, cover the pot and cook until the mussels have opened. Add the butter, lemon juice, parsley, and season with salt and pepper, to taste.
Heat remaining olive oil in a large saute pan over medium-high heat.
Season cod on both sides with salt and pepper. Sear, skin-side down until golden brown. Turn the fish over and continue cooking until just cooked through. Place cod in shallow bowls and ladle linguica-chickpea broth, over and around. Make sure each plate has 6 mussels. Garnish with more parsley.