In a food processor, add the shrimp, pork, soy sauce, sesame oil, cornstarch, salt, pepper, garlic, egg whites, ginger, green onions and lemon juice. Process until partly smooth but not completely pureed (it should have a little texture).
Hold a wonton wrapper in your hand. Dip a tablespoon measure in cold water and then scoop 1 tablespoon of the filling onto the center of a wrapper (dipping the spoon in cold water first will make the filling come off easier). Lightly moisten the edge of the wrapper with some water and fold over to form a half moon. Holding the edge in your hands, crimp and pinch around wrapper to create a fluted edge. Flatten the bottom so that the edge is facing upwards. Repeat for the remaining filling and wrappers.
Heat a saute pan over medium-high heat and add the peanut oil. Add the gyoza flat-side down to the pan, and cook until toasted, 2 to 3 minutes. Remove the pan from the heat and add 1/4 cup water. Return the pan to the heat and cover with a lid. Remove the lid and cook until the water evaporates and the gyoza are golden brown and crispy. Serve hot with soy sauce for dipping.