In a large pot, bring the chicken stock to a boil with the carrot and celery. Season with salt and pepper. Add the orzo and cook until al dente, about 7 minutes.
Meanwhile, in a bowl, knead the pork with the 1/4 cup of cheese, the bread crumbs and 1/2 teaspoon each of salt and pepper. Form the mixture into 1-inch balls.
Drop the balls into the boiling soup and simmer for 5 minutes. Stir in the spinach and chickpeas and simmer until the meatballs are cooked through, 5 minutes longer. Serve, passing extra cheese at the table.