Preheat the oven to 350 degrees. Grease a 9x13 pan or line with parchment paper. Combine the butter, sugar, molasses, and vanilla in a mixing bowl and beat with a mixer on medium speed until creamy. Add the egg and stir again. Add the flours, baking soda, spices, and salt. Mix until well combined.
Press the dough into the prepared pan, using either a spatula or your hands to smooth it to the edges of the pan. Bake for 15-20 minutes. A toothpick inserted should come out mostly clean, with wet crumbs. Cool in the pan on a wire rack.
When cooled, beat together the butter and cream cheese for the frosting. Add the powdered sugar and beat again until smooth and fluffy. Add the vanilla extract or vanilla bean and stir to mix throughout the frosting. Frost the bars, slice and serve. Store the bars in an airtight container in the refrigerator. Enjoy!