Bring a large cast-iron Dutch oven of water to a boil, salt it, and cook the orecchiette according to the package instructions to al dente. Drain and set aside.
1 pound orecchiette pasta
Wipe out the inside of the Dutch oven with a clean kitchen towel, heat the oil over medium heat. Add the sausage and cook until cooked through and browned, 5 to 7 minutes, breaking up large pieces of meat. Drain if you must.
1 pound bulk Italian sausage, 2 tablespoons olive oil
Add the spinach and chicken stock, cover, and cook for 2 to 3 minutes, until the spinach is wilted.
121 ounces baby spinach, ⅓ cup chicken stock
Fold in the pasta. Heat briefly to allow any excess liquid to evaporate, then fold in the mozzarella cheese and lemon zest. Top with Parmesan. Season with salt, add the giardiniera, and serve immediately.
1 cup mozzarella cheese, ½ cup grated Parmesan cheese, 2 teaspoons lemon zest, 2 tablespoons giardiniera