1 kabocha squash
3/4 c wheat flour
1 tsp corn starch
3/4 c cold water
Mix 3/4 of a cup of wheat flour and a teaspoon of corn starch with 3/4 of a cup of cold water (refrigerate the water beforehand or add ice cubes to room temperature water). Mix roughly. Place a deep-fry dish with roughly 1 1/2" of vegetable oil on a medium heat so that the oil reaches 320F. If you drop a little batter into the oil, it should sink to the bottom of the dish and then quickly float up to the surface. Put the sliced squash into the batter cover both sides. Deep fry each piece of squash for 1 – 2 minutes. Prod each piece of squash with chopsticks to check the batter feels crispy. Turn each piece over so that both sides are cooked evenly. Remove the squash from the oil and place on a draining tray. Sprinkle 2 – 3 pinches of the salt over the tempura and serve immediately!!
This is from the Japan Eats website