Preheat oven to 350 degrees and spray 12 muffin tins with nonstick spray. Place butter and sugar in a mixing bowl and beat at high speed with an electric mixer for 30 seconds. Add eggs and continue to beat until mixture is very fluffy. Add mashed sweet potatoes and grated ginger root and beat at medium until blended.

Sift flour, baking soda, baking powder, salt, cinnamon, nutmeg and allspice together. Fold in half of flour mixture. Stir in coconut milk. Fold in remaining flour mixture and crystallized ginger. The batter should be smooth, but be careful to not over mix. Fill prepared tins halfway with batter. Bake until muffins are golden brown and a toothpick inserted into center of a muffin comes out clean, about 25 minutes. Transfer muffin tins to a wire rack and cool for 10 minutes before removing muffins.