Preheat oven to 375 degrees F. Lightly grease a 13x9x2-inch baking pan; set aside. In a large bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add brown sugar, baking powder, cinnamon, ginger, baking soda, and salt; beat until combined.
Add molasses, the water, and eggs; beat until well mixed. Beat in all-purpose flour and whole wheat flour.
Spoon batter into prepared pan, spreading evenly. Bake about 20 minutes or until a toothpick inserted in the center comes out clean. Cool in pan on wire rack.
While bars are cooling, prepare Maple-Cream Icing. Spoon icing over uncut bars; spread evenly. Let stand until set. Cut into bars. Makes 32 bars.
In a medium bowl, stir together dairy sour cream, vanilla, and maple flavoring. Gradually whisk in powdered sugar, whisking until smooth.