Preheat your oven to 350°F (175°C). Grease and line a 9×13-inch baking pan with parchment paper, leaving a slight overhang for easy removal after baking.

In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger. This ensures the spices are evenly distributed before mixing with the wet ingredients.

In a large mixing bowl, whisk together the vegetable oil, granulated sugar, brown sugar, eggs, and vanilla extract until smooth and slightly thickened. The oil keeps the cake bars moist, while the mix of white and brown sugars adds sweetness and depth.

Gradually fold the dry mixture into the wet until just combined. Stir in the shredded carrots, and if you like extra texture, add the walnuts and raisins at this stage. Avoid overmixing to keep the bars tender.

Pour the batter into the prepared pan and spread it evenly with a spatula. Bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean. Let the bars cool completely in the pan before frosting.

In a medium bowl, beat the softened cream cheese and butter until smooth and fluffy. Gradually add powdered sugar and vanilla extract, mixing until light and creamy. This frosting is slightly tangy, perfectly sweet, and the ideal match for the spiced carrot cake.

Spread the frosting evenly over the cooled carrot cake bars, smoothing with a spatula or swirling for a decorative touch. Slice into squares or rectangles and serve. Store leftovers in an airtight container in the fridge for up to 5 days.