Finely chop the pork. Blanch the spinach stems, drain them, squeeze them to dry, and then finely chop them. Peel and finely chop the ginger. In a bowl, mix the pork, ginger, and soy sauce. Then, add the chopped spinach to obtain a filling. Place 1 tablespoon of filling, molded into a cylinder, in the center of a ravioli wrapper. Fold one side of the wrapper over the filling and slip the edge of this side under the filling. Roll up the wrapper, leaving a 1cm border. Pull the floating ends until they overlap slightly. Pinch these ends firmly to seal them. As the ravioli are made, place them on a plate and cover them with a damp cloth. Bring 2 liters of water to a boil in a large pot and add the ravioli. Bring the water back to a boil. Reduce the heat and cook for 5 minutes. The ravioli should remain slightly crunchy. Drain the ravioli in a colander. Discard the cooking water. Pour the broth into the pot and bring it quickly to a boil. Add the cress and ravioli. Bring back to a boil. Serve immediately.