How to Make It
In a deep skillet, add the oil, shallot and garlic and cook over moderate heat, stirring, until softened, 3 minutes. Add the tomatoes, thyme and a pinch each of salt and pepper. Cook, stirring, until the tomatoes start to break down, 4 minutes. Add the beans and stock and simmer until the beans are hot, 2 minutes. Add the escarole, prosciutto and lemon zest and cook over moderately high heat, stirring, until the escarole is just wilted, 4 minutes; if the bean ragù is too thick, add a little water.
Preheat the broiler. Line a rimmed baking sheet with foil and brush it with oil. Season the fish with salt and pepper and set on the baking sheet. In a bowl, whisk both mustards with the wine, 2 teaspoons of oil, the garlic, thyme and a pinch each of salt and pepper. Broil the salmon fillets 6 inches from the heat for 2 minutes, until the top just starts to brown. Spoon the mustard on the salmon and broil for 5 minutes, until the fish is nearly cooked through and the top is browned. Spoon the bean ragù into bowls, top with the fish and serve.