Preheat oven to 425 degrees. Line a baking sheet with parchment paper.
In a medium bowl, combine sour cream, kabocha puree, and egg. Set aside.
In the bowl of a food processor, pulse 6 tbsp sugar and candied ginger together until ginger is finely chopped. Add flour. Sift salt, baking powder, baking soda, and spices over flour mixture in food processor. Pulse until spices are evenly distributed. Add cold butter and pulse until butter pieces are thoroughly incorporated into dry ingredients.
Turn food processor contents into bowl with sour cream mixture. Stir until mixture clumps together.
Turn dough onto floured surface. Knead a few times and pat into an 8-inch circle. Cut into 8 wedges. Transfer carefully to prepared baking sheet, leaving 1/4" between pieces.
Bake for 18 minutes. Remove to a wire rack to cool.