How to Make It
Preheat the oven to 425°. In a medium saucepan of boiling salted water, cook the turnips and carrots until tender, 5 minutes; drain, transfer to a bowl and wipe out the saucepan. In the saucepan, heat 1 teaspoon of the olive oil. Add the pancetta and cook over moderate heat until the fat has rendered, about 4 minutes. Using a slotted spoon, transfer the pancetta to a plate. Add the turnips, carrots, scallion bulbs and hominy to the saucepan and cook over moderate heat, stirring occasionally, until richly glazed, about 8 minutes.
Cut enough of the scallion greens into 2-inch lengths to make 1/2 cup; finely chop the remaining greens to make 1 cup. Add the vegetable stock, the 1/2 cup of scallion greens and the parsley to the saucepan. Cover and simmer over low heat until the scallion bulbs are tender, about 2 minutes. Stir in the lemon juice, marjoram, thyme, allspice and cayenne. Stir in the butter, 1 tablespoon at a time, and season with salt and pepper. Cover the stew and remove from the heat.
In a skillet, heat the remaining 1 tablespoon of olive oil. Add the 1 cup of chopped scallion greens and cook over high heat until softened, about 1 minute. Scrape the scallion greens and oil into a medium bowl. Stir in the bread crumbs and pecans and season with salt and pepper. Arrange the catfish fillets on a large rimmed baking sheet and season with salt and pepper. Press the bread crumb mixture on each fillet to form a crust. Roast the fish on the top shelf of the oven for about 8 minutes, until the crust is crisp and the fish is just cooked through.
Gently reheat the hominy stew and spoon into shallow bowls. Scatter the reserved pancetta on top and serve with the catfish.