Sear mushrooms in a pan with 1 teaspoon vegetable oil. Set aside in a large bowl. Sprinkle leeks with extra salt and cook them in the other teaspoon of vegetable oil until very soft and starting to brown. Add them to the mushrooms and set aside.
To make the purée I peel the pumpkin with a Y-shaped vegetable peeler, scoop it out and cut it into 2-inch chunks. Sprinkle the pieces with salt and roast in a 425°F. until very soft. Let it cool and purée it in a food processor. Pumpkin can be frozen this way for later use.
Add the pumpkin purée, ½ teaspoon salt, sesame oil and sweet chili sauce to the mushroom-leek mixture. Using a microplane or other small grater, grate in the garlic. Mix well.
Place 1 teaspoon of the mixture in a wonton wrapper. Be careful not to overfill; less is best. Lightly moisten 2 sides of the wrapper and pinch shut into a triangle shape with your fingers or a wonton press. Continue this until all wrappers are filled. (You can freeze them in a single layer on a sheet tray for 24 hours and then put them in a zip-top bag for later use. They will keep this way for about 3 months).
To cook them, heat a nonstick pan (I like to use a ceramic-coated frying pan) over medium-low heat until very hot, add 1 teaspoon of oil or spray with nonstick spray. Place as many pot stickers as will fit in a single layer in the pan. Cook 2–3 minutes to brown, then flip them over to brown the other side. Once both sides are browned, add 2 tablespoons of water to the pan. Wait until the water has evaporated and serve with dipping sauce.
Dipping sauce: Add soy sauce, vinegar and maple to a small dish. Grate garlic into mixture. Stir and serve with wontons.
* To clean a leek I like to cut the tough green top off. Then cut the leek in half lengthwise and then cut the halves into 1-inch pieces that end up looking like half circles. Put these pieces in a large bowl and fill with cold water. Separate the leek pieces and swish around aggressively in the water. The clean leeks will float and the dirt will sink. Carefully scoop the leeks out and place in a colander to drain, leaving the dirty water behind in the bowl.