Wash the kabocha pumpkin thoroughly, remove the skin and seeds, then steam it.
Mash the steamed kabocha pumpkin and let it cool.
Mix flour, sugar, salt, and yeast together with the kabocha pumpkin.
Add butter and milk, then knead the dough.
Cover the dough with plastic wrap and let it rise for about 1 hour.
Shape the dough as desired and place on a baking pan.
Bake in a preheated oven at 180°C (356°F) for 25 minutes.