2. Place the butter in a mixing bowl and beat at high speed with an electric mixer for 30 seconds. Gradually add the sugar and continue to beat until the mixture is very fluffy.
3. Add the egg and mix on low speed to combine. Add the pumpkin puree and grated ginger root and mix again.
4. Sift the flour, baking soda, baking powder, salt, cinnamon, nutmeg and allspice together.
5. Fold in half of the flour mixture. Stir in the buttermilk. Fold in the remaining flour mixture and the crystallized ginger. The batter should be smooth, but be careful to not overmix.
6. Fill the prepared tins halfway with the batter. Bake until the muffins are golden brown and a toothpick inserted into the center of a muffin comes out clean, about 25 minutes.
7. Transfer the muffin tins to a wire rack and cool for 10 minutes before removing the muffins.