Oyaki (Japanese Stuffed Dumplings)

Name: Oyaki (Japanese Stuffed Dumplings)
Prep time: 1 h 10 min
Cook time: 45 min
Total time: 1 h 55 min
Cuisine: Japanese
Ingredients: 2½ cups all-purpose flour (plain flour); 200 ml boiling water ((1 cup minus 2½ Tbsp)); 1 tsp neutral oil; ¼ tsp Diamond Crystal kosher salt (use half the amount or the same weight for table salt); 2 Japanese or Chinese eggplants; 1 Tbsp toasted sesame oil; 1 Tbsp sugar ((you can reduce if you‘d like; the dough tastes rather bland, so make sure the filling has a strong flavor)); 1 Tbsp miso; 2 shiso leaves (perilla/ooba) ((julienned; optional)); 12 oz kabocha squash ((¼ kabocha with seeds)); 1 Tbsp neutral oil; ¼ cup water; 1 Tbsp sugar; 1 tsp soy sauce; 1 pinch Diamond Crystal kosher salt (use half the amount or the same weight for table salt)