Wash the kabocha squash thoroughly, remove the seeds, and peel it.
Cut the kabocha squash into small pieces and steam them.
Mash the steamed kabocha squash smoothly and let it cool.
Add cake flour, sugar, salt, instant dry yeast, milk, egg, and melted butter to the mashed kabocha squash and knead the dough.
Let the dough rise for the first proofing.
Divide the proofed dough and shape into round balls.
Place them on a pan or oven tray for the second proofing.
Bake in a preheated oven at 180°C for 20 minutes.