Stir the suet into the flour with the herbs, salt and pepper. Press about 6 tablespoons of juice from the cooked spinach (or pour off the water from frozen spinach and then press it well). Stir the green liquid into the flour mixture to make a stiff dough and knead it a little. Divide the dough to make walnutsized balls. Set aside in a cool place.
Ten minutes before the dumplings are to be eaten, have about 5 cups (1.2 litres) of salted water boiling in a large saucepan. Drop the dumplings in and boil briskly (but not so hard that they will break up). Do not let the water go off the boil. Lift the little green balls out with a perforated spoon.