Place the flour and salt in a large bowl; mix until well combined. Make a well in the center and pour in the hot water. Using a spatula, fold in all the flour until a shaggy dough forms with no apparent dry spots of flour. If there is, add cold water, one tablespoon at a time. 

Transfer the dough onto a clean surface. Knead into a dough for about 10 to 12 minutes. Cover with a damp towel and let it rest for 30 minutes.

Heat 2 teaspoons neutral oil in a non-stick skillet.Add the chopped green beans and sauté for 2 to 3 minutes until the beans turn to a darker green. Place the cooked green beans into a bowl along with the mashed potatoes, carrot, cilantro, sesame oil, salt and pepper. 

Mix until well combined. Divide the mixture into 10 portions. Form each portion into a patty-like shape.

When the dough is ready, dust your work surface with flour and roll the dough out into a log. Divide into 10 equal portions. Set aside.

To form a wrapper, take one portion of dough and flatten it with the palm of your hand. Hold the wrapper with your non-dominant hand and a roller with your dominant hand. Roll the dough by pushing from the outside towards the middle of the wrapper. Twist and turn your wrapper while doing this (with your non-dominant hand). Roll it into a 4.5 inches diameter disc.

With this rolling method, the middle of the wrapper is thicker which creates a good safety net for the filling. Place one filling patty in the middle and pleat to seal. Continue to form the remaining buns with the rest of the ingredients.

Dab the smooth side of each bun with water and gently press on some sesame seeds.

To cook the buns potsticker-style, heat a large non-stick pan with a tablespoon of neutral oil. Gently flatten each bun with the palm of your hand and place them in the pan, sesame side down, slightly apart. Fit as many as you can in one layer.

Cook until the bottom turns golden brown, then flip the buns and add about a cup of water so that it covers not quite half the height of the buns. Cover the pan with a tight-fitting lid, preferably glass, and turn heat to low-medium. Cook until all water has completely evaporated, about 5 to 10 minutes.

If you prefer to cook the buns in the oven, preheat oven to 375°F (195°C) and brush the buns with oil. Bake the buns for about 20 to 25 mins or until golden brown, flipping halfway through.

Garnish with a handful of chopped green onions. Best when served immediately, while still warm with some soy sauce on the side.

For a super delicious (a bit spicy) dipping sauce, combine 1 tablespoon soy sauce, 2 teaspoons rice vinegar, 1 teaspoon honey, 2 teaspoons sesame oil, and 1 teaspoon gochujang (Korean chili sauce)