Monkfish and Clam Bourride

Quarter potatoes, then cover by 1 inch with salted cold water in a 3-quart saucepan and simmer, covered, until just tender, 7 to 10 minutes. Drain in a colander, then cool.

Wash leeks in a bowl of cold water, agitating water to loosen any sand, and lift leeks from water to a sieve to drain. Pat dry.

Pat monkfish dry and season with salt and pepper. Heat oil in a deep 12-inch heavy skillet over moderately high heat until hot but not smoking, then sear monkfish lightly on all sides until golden, about 2 minutes total (fish will not be cooked through). Transfer fish to a plate using tongs.

Heat 2 tablespoons oil from slow-braised tomatoes in skillet over moderately high heat until hot but not smoking, then sauté leeks, fennel, and shallots, stirring, until softened and edges begin to brown, 4 to 6 minutes. Add sliced garlic and sauté, stirring, until fragrant, about 2 minutes.

Add clams, wine, water, red pepper flakes, zest, and tomato halves and cook, covered, until clams are fully open, 6 to 10 minutes, checking every minute after 6 minutes and removing clams as they fully open. (Discard any clams that have not opened after 10 minutes.) Using tongs, transfer clams to a large bowl or soup tureen.

Add monkfish and potatoes to skillet and simmer, covered, until fish is just cooked through, 4 to 6 minutes. Remove from heat and stir in basil and parsley. Season with salt and pour over clams.

While monkfish is cooking, rub one side of each toast with a cut side of halved garlic clove. Divide bourride among 4 shallow bowls. Add a garlic toast and top with a spoonful each of aïoli and tapenade.