In a skillet, combine all the ingredients up to and including the wine. Sauté over medium heat, breaking the pork sausage up as it cooks to prevent clumping. Cook until all the pink has gone. Pour off any excess fat
In turn, stir in the spinach, then the cornstarch-water mixture, then (slowly, while stirring) about two-thirds of the beaten egg. Remove the pan from the heat, scoop the mixture into a bowl and set aside.
Separate a few gyoza wrappers (this is tricky: be sure they're only one layer thick) and place on a cutting board. With a brush, apply a semicircle of beaten egg along the top margin of each wrapper. Spoon a scant teaspoon of the pork mixture in the center, then carefully fold the wrappers over and press the edges together. Seal the edges as completely as possible without breaking the wrappers. Place the finished dumplings on a platter, and cover them with a damp cloth to prevent their drying out while you assemble the rest of the dumplings.
You can boil the dumplings in about an inch of simmering water, but steaming over a simmering pot works better. In either case, cook only until the noodles become translucent. At that point, the dumplings are completely ready to be eaten, but you can add further excitement with the pot-sticking trick.
Heat a tablespoon and a half of oil in a skillet over medium-high heat. Space out as many dumplings as the pan will hold and cook until they're crispy brown on one side (this is when they stick to the pot). Turn them to crisp the other side, then remove and keep warm. Add a little more oil between each batch, and continue cooking until all are done.
Mix the ingredients for the sauce. Stir well before each serving (because the pepper oil will float to the top). Each person should spoon his or her sauce over the dumplings.