Steam the sweet potatoes (you can also do this in a microwave) and mash whilst they are still hot. Peel the kabocha and remove the seeds. Cut into smaller pieces and microwave. Strain the kabocha squash and the sweet potatoes if you like.
In a bowl, add the sweet potato, kabocha squash, sugar, skimmed milk and milk and blend together with a wooden spatula.
Shape the mixture into bite-size pieces. Brush over a glaze made from 1 egg yolk and 1/2 tablespoon water and bake in an oven preheated to 200°C for 15 minutes. When they have browned, they're done.
Story Behind this Recipe
I thought about making sweet potato bites that I could eat even when I'm on a diet. Because I didn't add egg yolks, the color was off, but it improved dramatically when I added kabocha squash.
Please adjust the amount of milk according to the amount of water in the sweet potatoes and kabocha. These aren't very sweet, but you could increase the amount of sugar if you like. Steaming the sweet potatoes will make them sweeter than microwaving, so I recommend steaming. It's ok if you don't strain the sweet potatoes but if you want a nice colour, strain the kabocha squash.