Preheat the oven to 350F. To begin, add the oat milk and apple cider vinegar to a mixing bowl and let sit 5-10 minutes until the milk begins to separate & curde. While the vegan buttermilk is forming, grate the carrots and set aside.
Once the vegan buttermilk is ready, add in the rest of the wet ingredients including the grated carrot, maple syrup, coconut sugar, oil, and vanilla. Gently whisk to combine.
Next, use a flour sifter to add in the dry ingredients including the whole wheat flour, cinnamon, salt, baking powder, and baking soda. Gently mix until a thick cake batter forms, but try not to overmix. Then, gently fold in the chopped walnuts using a spatula or spoon.
Pour the carrot cake batter into a 8-inch springform pan or greased 8 or 9-inch pan and tap the pan to level the cake batter. Then, add the cake to the oven and bake for 30 minutes until lightly browned on the outside and cooked through. Remove the cake and let cool before frosting.
While the carrot cake is cooling, make the cashew frosting. Add the soaked cashews, coconut cream, maple syrup, coconut oil, lemon juice, and vanilla to a blender. Blend on high speed until the frosting is completely smooth, stopping to scrape down the sides as needed. Then, place the cashew frosting into a container into the fridge for at least 15 minutes to firm up before frosting.
Once the cake has cooled and the frosting has firmed, frost the cake! Top with extra walnuts and carrots as garnish. Enjoy!