Oven at 375°F, middle rack, ungreased sheet. Drop by the tablespoon and bake 10 minutes. Sprinkle with granulated sugar while still hot, cool 2 minutes on the sheet, then finish on a wire rack.
For sprinkling
Preheat to 375°F with the rack in the middle position.
Sift the flour, baking soda, salt, cinnamon, and ground ginger into a medium bowl. Whisk together to mix thoroughly.
In a large bowl, beat the butter, shortening, and sour cream until smooth.
Add the sugar, molasses, and fresh grated ginger. Add the egg and beat on medium to combine. Gradually beat in the flour mixture.
Using a tablespoon, space dollops evenly on an ungreased cookie sheet. Bake 10 minutes.
Sprinkle lightly with granulated sugar and cool 2 minutes on the sheet. Cool completely on a wire rack.
The butter was warmed on the counter, but not quite to room temperature. Eggs were at room temperature.