To make the mashed potatoes, combine the hot water, butter, salt and cold milk together in a bowl. Stir in the instant potatoes, and allow them to sit for about a minute. Fluff the potatoes with a fork and allow them to cool completely. This can be done the day before.
To make the filling, make sure the potatoes are at room temperature.
In a small pan, heat the vegetable oil over medium heat and add the chilies. Gently heat the chilies for 15-30 seconds. Add the garlic and ginger, then cook for an additional 1-2 minutes or until fragrant. Remove from the heat and stir in the green onions, soy sauce and sesame oil. Allow this mixture to cool for 3-5 minutes and then stir into the prepared room temperature mashed potatoes.
Make sure the wonton wrappers are thawed. In a small bowl, combine the water with the flour to make a small slurry.
Take about a tablespoon of filling and place it in the center of each wonton. Making sure to keep the other wontons loosely covered with the damp towel to prevent them from drying out.
Lightly brush two edges of the wonton wrapper with the slurry and fold it into a triangle to seal, making sure to squeeze any air out of the dumpling. Set aside and repeat with the other dumplings. This can be done ahead of time, and these can even be frozen on a baking sheet until completely frozen, then transferred to a resealable plastic bag and held in the freezer until ready to use.
To make the ginger scallion sauce, heat the vegetable oil to 350°F. Add the ginger and cook for 5-10 seconds, remove from the heat and add the garlic and the green onions. Add the salt and add in the sesame oil.
To cook the wontons, simply bring a pot of water to a boil and cook them until they float. Drain the dumplings well and drizzle with the scallion sauce. Serve immediately.
