1. Heat oven to 400 degrees . Line a baking sheet with parchment paper or a silicone baking-sheet liner.
2. Combine flour, 2/3 cup of the sugar, the baking powder, baking soda, salt and 1/2 teaspoon of the crystallized ginger in a large bowl. Add butter; mix with pastry blender until mixture resembles coarse crumbs. In a small bowl, whisk together pumpkin, buttermilk and egg. Gently stir into dough, along with raisins.
3. Drop dough by 1/2-cupfuls onto prepared sheet, about 2 inches apart. In a small bowl, stir together remaining tablespoon sugar and remaining 1/2 teaspoon chopped crystallized ginger. Sprinkle sugar-ginger mixture evenly over dough.
4. Bake at 400 degrees for 16 minutes or until golden brown. Remove to wire rack and let cool slightly. Serve warm or at room temperature.