Slice the skin off the kabocha. I find it easiest to cut the kabocha in half and then into long pieces (like cutting a melon) and slicing the skin off at this point. For the completely mashed kabocha, place the kabocha pieces in a microwave safe bowl, wrap the top in saran wrap and place in the microwave for about 3 minutes. Check the kabocha by gently pressing on it through the saran and if not soft yet, cook more in about 30-45 second intervals until completely soft. Once soft, mash it up and set aside!