Preheat oven to 350°. Line 24 muffin cups with paper liners.
Cream butter and brown sugar together in a large bowl with an electric mixer until combined. Add water and molasses and beat until combined. Add eggs and continue to beat until combined.
1 cup butter, 1 cup brown sugar, 1 cup water, 1 cup molasses, 2 eggs
Mix flour, baking powder, baking soda, salt, cinnamon, ginger, nutmeg and allspice in a medium bowl until combined. Beat into wet mixture until well combined.