In a medium bowl - combine flour, baking soda, ginger, cinnamon, cloves, allspice and salt. Set aside.
Using a hand mixer, cream butter and brown sugar in a separate medium bowl until light and fluffy, 2 to 3 minutes.
Add eggs and beat until incorporated.
Combine molasses and water, then add to batter.
Mix until just combined, scrape down bowl.
Add flour mixture and beat until just combined - do not overmix.
Pour into prepared pan and bake for 45 - 50 minutes or until a toothpick inserted comes out with a few moist crumbs attached.
Cool in pan for 10 minutes. Carefully remove gingerbread loaf from pan. Place on cooling rack to cool completely before glazing.
Make maple bourbon glaze
In a small bowl, whisk together powdered sugar, maple syrup, bourbon, vanilla and salt (if using). Adjust to desired consistency, if needed, by adding more sugar or maple syrup.
Pour over completely cooled gingerbread loaf. Let icing set for at least an hour to harden before slicing.
Notes
• To glaze the loaf of gingerbread, set the cooling rack inside of a baking sheet to catch the excess glaze.