Cut the kabocha squash in half and remove the seeds.
Place the kabocha squash with the skin in a steamer and steam for 20 minutes. Scoop out the flesh.
Season the inside of the squash with salt and pepper.
Melt butter in a pan and sauté chopped onions.
In a bowl, mix eggs, sautéed onions, milk, salt, and pepper.
Pour the egg mixture into the squash.
Top with cheese and bake in the oven at 180°C for 10–15 minutes.
Sprinkle parsley on top of the baked kabocha squash to finish.