First, start out by sifting and whisking all the dry ingredients (flour, cinnamon, nutmeg, baking soda, and baking powder) together in a medium mixing bowl until well mixed. Set this bowl aside until we're ready to use it.

Second, rinse, peel, and grate the carrots, then set these aside also.

After that, preheat your oven to 350 F (180 C).

Next, add the eggs and sugar to a large mixing bowl and whip it on high with an electric mixer for 15 minutes. Reduce the mixer speed to medium, then add the vanilla extract and buttermilk. Continue mixing for another minute or so at medium speed.

Now, grab the dry ingredients we mixed earlier, the grated carrots, and a rubber spatula. We're going to gently fold in 1/3 of the dry ingredients, then 1/3 of the grated carrots, and continue doing this until all of it is well combined.

Try not to deflate any air pockets in the batter while you're folding the ingredients in. This will help make our cake light and fluffy when we bake it.

Divide the batter evenly into two baking sheets greased with butter or cooking spray and lined with parchment paper.

Bake both pans of batter at 350 F (180 C) for 25 – 30 minutes or until you can insert a toothpick in the middle and it comes out clean.

Remove the cakes from the oven and let them cool for a couple of minutes, enough to handle them without burning yourself.

Take the cakes out of the pans and dust the tops of them with powdered sugar. Roll them both into logs and let them cool completely on a wire rack before dividing and frosting them.

First, make sure your cream cheese is warmed to room temperature. Whip it on high for one minute in a medium mixing bowl, scraping the sides of the bowl halfway through.

Add the butter and beat it on high again until it's well mixed with the cream cheese.

Now add the sugar and beat it again until the sugar is dissolved and all three ingredients are well combined.

Next, add cold heavy whipping cream and continue beating at high speed. The frosting will become very thin at first, then start forming into a thick mixture.

As soon as the mixture starts thickening, scrape down the sides of the bowl to ensure all the ingredients are properly incorporated, and whip for another 30 seconds.

Finally, add the vanilla extract and a pinch of cinnamon and beat again for another 15 seconds.

Carefully unroll the cake logs we made earlier, then split each sheet of cake in half vertically. You should have four, 6" x 16" inch rectangles.

Next, use a half-cup ice cream scoop to place frosting on each of the 4 strips of sponge cake. Use a spatula to spread the frosting out evenly.

Now we're going to re-roll the cakes, using 2 strips per roll. Line up the short ends of the cake, roll the first strip tightly but gently so the cake doesn't break, then roll the first roll up in the second strip, making one large roll.

Flip the cake log upright and spread some leftover frosting over the tops of the cakes. Refrigerate the rolls for 4 hours or overnight before frosting the outer layer.

After the outer layer is frosted, spread any remaining frosting on the top and sprinkle chopped walnuts on the very edge of the cake. Let the cake sit in the fridge for a couple more hours to make sure all the frosting is set.