Place the black-eyed peas, shallot halves, carrot, celery, and 3 thyme sprigs in a large saucepan. Cover with water by 1 inch. Simmer over medium heat until the peas are tender. Let cool to room temperature in the cooking liquid.

In a large, deep skillet, add oil and the pancetta and cook over moderate heat, stirring frequently, until slightly crisp and browned, about 7 minutes. Using a slotted spoon, transfer the pancetta to a plate.

Add the minced shallots to the skillet. Cook over moderate heat, stirring occasionally, until softened and just beginning to brown. Add the garlic and cook briefly, then add the cabbage and chopped thyme. Season with salt and pepper. Cook, stirring occasionally, until the cabbage is very tender, about 20 minutes. Stir in a little of the black-eyed pea cooking liquid to keep the cabbage from scorching.

Meanwhile, bring a large pot of salted water to a boil. Add the pasta and cook until al dente. Drain, reserving 1 cup of the cooking liquid.

Combine the black-eyed peas with the cabbage. Add the drained pasta and a little of the pasta cooking liquid to the cabbage mixture. Cook, stirring, until the liquid is absorbed and the pasta is coated in a lightly creamy sauce. Stir in the pancetta and serve. Garnish with Pecorino Romano.