Make the Batter: Combine the dry ingredients in a bowl. Gradually add the club soda, stirring until the batter is smooth.
Coat the Pumpkin: Cut the kabocha squash in half and remove the seeds. Then cut the pumpkin into individual slices, approximately ¼ inch thick. Dip into the batter, coating each piece fully.
Fry the Pumpkin: Pour a mild-flavored oil into a pot and heat over medium heat until it reaches about 350°F. Carefully place each coated piece of kabocha squash into the hot oil and fry until golden brown.
Serve: Once the pumpkin slices are golden brown, remove them from the hot oil and place on a paper towel to drain. Serve immediately while they are still warm.
Notes
If you don’t have a cooking thermometer, test the oil by dropping in a small bit of batter—if it sizzles immediately and floats to the surface, the oil is ready.
Fry the pumpkin in batches, leaving enough space around each slice to ensure they fry evenly. Overcrowding can cause the slices to stick together or turn soggy where they touch.