Preheat oven to 325-f degrees. Line an 8x8-inch baking pan with foil and lightly spray with cooking spray.
Cream the butter and sugar for 2 minutes. Add egg, molasses and vanilla and stir well. Add the spices and flour together in a bowl. Mix the dry ingredients with the creamed butter and sugar. Mixture will be very thick.
Add to the prepared baking pan and pat it in evenly to cover the pan.
Bake for 25 minutes, removing when the edges are starting to turn brown. Set aside to cool.
To make the glaze, combine all ingredients in a mixing bowl and blend with a hand mixer until no clumps of powdered sugar remain. When the gingerbread bars have cooled, add the glaze to the tops and set aside to let set up a bit. Glaze will remain fairly soft.