1. Grease bottoms of twelve 2 1/2-inch muffin cups; set aside.
2. In a medium bowl, combine flour, fresh or ground ginger, baking powder, allspice or cinnamon, baking soda and salt. Cut in butter until mixture resembles coarse crumbs.
3. In another medium bowl, stir together milk, egg, sour cream, brown sugar and molasses. Add egg mixture all at once to the flour mixture. Stir just until moistened (batter should be a little lumpy).
4. Spoon batter into the prepared muffin cups, filling each nearly full. In a small bowl combine granulated sugar and crystallized ginger. Sprinkle over the muffin batter.
5. Bake in a 400°F oven for 18 to 20 minutes or until golden and a wooden toothpick inserted near the centers comes out clean. Cool in muffin cups on a wire rack for 5 minutes. Remove from muffin cups; serve warm.