Place an oven rack in the center position and preheat the oven to 350°F (176°C).

Prepare two 9-inch round cake pans by greasing them, lining the bottoms with parchment paper, and greasing the top again. Alternatively, grease and flour both the sides and bottom of the pans.

In a medium-sized bowl, combine the flour, baking soda, salt, and cinnamon. Whisk until thoroughly mixed.

In a separate large bowl, blend the vegetable oil, granulated sugar, brown sugar, and vanilla extract until well mixed.

Add the eggs one at a time, whisking thoroughly after each addition.

Using a large rubber spatula, scrape the sides and bottom of the bowl, then gradually incorporate the dry ingredients in three parts, stirring gently until the mixture is smooth.

Fold in the grated carrots, chopped pecans, and raisins until evenly distributed.

Divide the batter evenly between the prepared cake pans. Bake for 35 to 45 minutes, or until the tops of the cakes are springy to the touch and a toothpick inserted in the center comes out clean.

Allow the cakes to cool in the pans for 15 minutes. Then, carefully transfer the cakes to cooling racks, remove the parchment paper, and cool completely.

In a large mixing bowl, beat the cream cheese with a handheld mixer on medium speed until smooth, about 1 minute.

Gradually add the powdered sugar and cornstarch (if using), sifting them over the cream cheese to avoid lumps. If sifting isn't possible, add in increments of ¼ cup at a time, mixing until smooth.

Pour in the cold heavy cream and beat on medium speed for 2 to 3 minutes, until the frosting achieves a light, fluffy consistency similar to whipped cream. Cover and refrigerate until ready to use.

Once the cake layers have cooled completely, spread a layer of frosting on the top of one cake. Place the second layer on top.

Spread the remaining frosting on top, using a spatula or butter knife to create decorative swirls. Leave the sides unfrosted for a rustic appearance. Garnish with chopped pecans.

The frosted carrot cake can be stored in the refrigerator for up to one week, covered with plastic wrap or in a cake keeper. Avoid freezing the frosted cake, as the frosting may not thaw well.

Unfrosted cake layers can be refrigerated for up to five days or frozen for up to three months. If frozen, thaw in the refrigerator overnight before frosting.