Rinse the kabocha, and without blotting dry, wrap in plastic (without cutting) and microwave for 3 minutes. Chop into suitably sized pieces, and steam for 10 minutes on medium heat.
Separate the skin and the flesh, and mash the flesh. Weigh the amount of flesh, wrap, and then freeze. It's convenient if you write the weight on the plastic wrap. Now you have handy frozen kabocha to use for cooking or baking.
Don't toss the skin and mix it in cake salé, toss it with mayonnaise, or put it in curry or gratin.
Story Behind this Recipe
I use a ton of kabocha in my cooking, so this method of storing it has been useful.
Although steaming takes extra effort, it definitely makes the kabocha more dense and floury.