Put butter in a large heatproof bowl and melt by microwaving. Combine flour and mix well.
Add milk to bowl from step 1 in small batches. When all the milk is combined, microwave for about 1 minute, mixing occasionally.
When it's thick, season with miso and pepper.
Slice kabocha into 5 mm pieces. Slice the onion.
Put the kabocha and onion into a heatproof container, cover with plastic wrap and microwave for 5 minutes. It's done when the kabocha is softened.
Combine condiments from step 3 with kabocha from step 5.
Put into a cocotte and top with cheese. Bake in 180℃ oven for 10 minutes.
Story Behind this Recipe
I usually make potatoes au gratin, but I thought it might be tasty if I used kabocha instead, and here it is!
Please peel the skin if it bothers you. You could also stir-fry with a frying pan in step 5! If you microwave it, you can reduce calories because you don't need oil. It's absolutely delicious with lots of cheese.