Preheat oven to 400 degrees F.
Place kabocha squash on a baking sheet and roast in oven until a knife can easily pierce through. Cut squash in half and scoop out seeds. Scoop out 1 cup of the squash meat, reserving the rest for another time. Mash squash until smooth and let cool.
Make sweet chili sauce. Combine chili oil with soy sauce, black vinegar, sugar, and garlic cloves in a small pot. Bring to a simmer over low heat and simmer until sugar has melted, about 1-2 minutes. Remove from heat and set aside.
In a large bowl, combine mashed squash with ground chicken, scallions, ginger, garlic, egg white, Shaoxing wine, soy sauce, sesame oil, coriander, salt, pepper, and cinnamon. Mix until well combined.
Assemble wontons. Working with one wonton wrapper at a time, place 2 teaspoons filling in the center. Brush water around the edges with your finger and gather the four corners towards the center to create little pouches. Pinch to seal. Place on a lined baking sheet lightly dusted with flour and repeat with remaining wraps and filling.
Bring a large pot of water to a boil over medium-high heat. Add wontons a few at a time and cook until they float to the surface. Remove with a slotted spoon.
Spoon a generous amount of sweet chili sauce in the bottom of a serving bowl. Place wontons on top and drizzle extra sauce on top. Garnish with sliced scallions and sesame seeds. Serve immediately.