How to Make It
In a large enameled cast-iron casserole, heat the olive oil. Add the onions, fennel, leek, garlic and chiles and cook over moderately low heat, stirring occasionally, until softened but not browned, about 15 minutes.
Add the anchovy paste and chile powder to the casserole and cook, stirring, until the anchovy dissolves, about 3 minutes. Stir in the collard greens and cook until just wilted, about 3 minutes. Add the fish stock and 4 cups of water and bring to a boil. Stir in the tomatoes and mushrooms and simmer over moderately low heat until the collards are just tender and the tomatoes start to soften, about 5 minutes. Add the fish and simmer until just cooked through, about 7 minutes; season with salt and pepper. Ladle the stew into bowls and serve with lemon wedges and crusty bread.
New Mexican Hatch green chile powder has a bright, floral, fruity flavor. It is available at gourmet markets and hatchnmgreenchile.com.