Preheat your oven to 350°F (175°C) and adjust the oven rack to the middle position. Grease a 9x13-inch jelly roll pan with non-stick cooking spray and set it aside.

In a large mixing bowl, whisk together the all-purpose flour, baking soda, cinnamon, ginger, nutmeg, cloves, and salt. Ensure the spices are evenly distributed for a balanced flavor. Set aside.

Using a stand mixer fitted with a paddle attachment or a large mixing bowl with handheld beaters, cream together the melted butter, granulated sugar, brown sugar, vanilla extract, and molasses on medium speed until the mixture is light and fluffy, approximately 2–3 minutes.

Add the egg to the creamed mixture and mix on low speed until fully combined. Scrape down the sides of the bowl as needed to ensure uniform mixing.

Gradually add the dry ingredients to the wet mixture, pulsing the mixer or beaters on low speed to avoid overmixing. Once incorporated, increase the speed to medium and mix until the dough is smooth and evenly combined.

Spread the dough evenly into the prepared jelly roll pan, smoothing the surface with a spatula. Bake for 15–20 minutes or until the bars are a rich golden brown and a toothpick inserted in the center comes out with just a few moist crumbs. Avoid overbaking to maintain a soft texture.

Remove the pan from the oven and transfer it to a wire rack. Allow the cookie bars to cool completely before applying frosting, approximately 1 hour.

In a clean mixing bowl, beat the softened cream cheese and butter on medium speed until smooth and creamy, about 2–3 minutes. Gradually add the powdered sugar and vanilla extract, mixing on low speed to combine. Increase the speed to medium-high and beat until the frosting is light and fluffy, approximately 1–2 minutes.

Once the bars are fully cooled, spread the frosting evenly over the surface using an offset spatula or knife. Garnish with holiday sprinkles if desired.

Cut the frosted bars into 24 equal squares and serve immediately, or store as needed.