Heat oven to 375.
Line muffin pan with liners.
Beat together sugar, butter, molasses, water and eggs on medium speed.
Whisk together flour, baking soda, salt, ginger, cinnamon and allspice.
Add dry ingredients into wet ingredients and mix until combined.
Spoon about 1/4 cup batter into each cup.
Bake 16-18 minutes or until toothpick inserted in middle comes out clean.
Allow to sit in muffin pan for 5 minutes before moving to cooling racks to finish.
Beat cream cheese until smooth, scraping down sides as needed.
Add butter and continue beating until mixture is blended and smooth.
Add vanilla and brown sugar and beat for 5 minutes until sugar is dissolved and frosting is light and fluffy.
Transfer icing to piping bag with star tip and frost tops of each cupcake.
Place in refrigerator for 30 minutes to firm icing.
You can optionally top with a gingerbread man cookie as garnish.