Preheat the oven to 350°F (180°C). Spray two 7 inch cake pans (*see notes) with non-stick spray and cut out circles of parchment paper line the bottoms.
Sift the flour into a mixing bowl and add the light brown sugar, white granulated sugar, baking soda, baking powder, salt, cinnamon, nutmeg, ginger and cloves.
Prepare your flax egg by adding 1 Tbsp ground flaxseed meal to a bowl and then adding in 3 Tbsp of Hot Water and allowing to sit for a minute to become gloopy.
Add the flax egg, pumpkin purée, oil, vinegar and vanilla to the mixing bowl and mix into a batter. Don't overmix.
Divide the batter equally between the prepared cake pans.
Place into the oven and bake for 30 minutes or until a toothpick inserted into the center of the cakes comes out clean.
Transfer to a wire cooling rack and allow to cool completely before frosting.
Prepare your frosting by adding the vegan butter, powdered sugar, vanilla and soy milk to the bowl of an electric mixer. Starting at slow speed, gradually increase the speed until the frosting is thick and smooth. If your frosting is too thick, add in soy milk a drop at a time until it reaches the right consistency.
Add the cinnamon last and mix on low until just mixed in.
When your cakes are completely cooled, frost them and then sprinkle cinnamon and crushed walnuts on top.