Preheat the oven to 350°F. Line and grease two 8″ pans.
In a measuring cup or small bowl, whisk the milk and vinegar. Set aside for 10-15 minutes.
In a medium mixing bowl, whisk the flour, baking soda and powder, salt, cinnamon, and nutmeg.
In a large mixing bowl, add the brown sugar, sugar, sour cream, oil, vanilla, and milk mixture and mix. Add in the dry mixture and blend until combined.
Fold in the carrots.
Pour even amounts of batter into each of your pans. Bake for 30-35 minutes, until a toothpick comes out clean.
Make the frosting:
In a large mixing bowl, add the buttery sicks and cream cheese. Beat until fluffy.
Slowly add the powdered sugar and beat.
Beat in the vanilla.
Add nondairy milk as necessary to reach desired consistency.
Assemble the cake:
Once the cake layers are chilled, pipe or spread buttercream on top of the first layer, then top with another cake layer. Top with a final layer of buttercream. Decorate with walnuts, if desired!
Notes
*Measure your flour using this method.**We highly recommend shredding carrots yourself for this recipe rather than using pre-shredded.***You want your butter and cream cheese to be soft enough so that they easily beat together. We recommend removing them from the fridge at least 30 minutes before using.