The oven should be preheated to 350°F (175°C). A 9×13-inch baking pan should be greased with non-stick cooking spray, then lined with parchment paper, leaving a little overhang on the sides for easy lifting. This step ensures clean, professional-looking bars every single time.

In a large mixing bowl, the vegetable oil, granulated sugar, and brown sugar are whisked together until fully combined. Next, the eggs are added one at a time, with the mixture being whisked after each addition. The vanilla extract is then stirred in. The result should be a smooth, pale golden mixture.

In a separate medium bowl, the flour, baking soda, baking powder, salt, cinnamon, nutmeg, and ginger are whisked together thoroughly. Combining the dry ingredients separately ensures that the leavening agents and spices are evenly distributed throughout the batter — a step that is critical to consistent, perfectly risen bars.

The dry ingredients are gradually stirred into the wet ingredients until just combined. Care should be taken not to overmix, as overmixing can result in dense, tough bars. Finally, the freshly grated carrots (and optional nuts) are folded in gently with a rubber spatula.

The batter is poured evenly into the prepared pan and smoothed out with a spatula. The pan is placed on the center rack of the preheated oven and baked for 25 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs. The bars should not be overbaked, as they will continue to firm up slightly as they cool.

The pan is transferred to a wire rack and allowed to cool completely — this step is non-negotiable. Attempting to frost warm bars will result in the cream cheese frosting melting and sliding off. Patience is rewarded here! The bars typically cool to room temperature within 45 minutes to 1 hour.

The softened cream cheese and butter are beaten together with a hand mixer or stand mixer on medium speed until light and fluffy, about 2 to 3 minutes. The vanilla extract and pinch of salt are then added. The sifted powdered sugar is added one cup at a time, with the mixer running on low speed. Once all sugar has been incorporated, the speed is increased to medium-high and the frosting is beaten for an additional minute until it is silky-smooth and spreadable.

The cream cheese frosting is spread generously and evenly over the completely cooled bars using an offset spatula. For a decorative touch, small carrot shapes can be piped on top using orange and green tinted frosting. The bars are then sliced into 16 equal pieces and served!