Preheat the oven: Preheat to 180°C fan (350°F).
Prepare the tins: Grease and line two 20cm (8-inch) round cake tins with baking parchment on the base and sides. Use coconut oil or plant-based butter to help the parchment stick.
Mix the dry ingredients: In a large bowl, sieve the self-raising flour. Add the caster sugar, grated carrot, raisins, walnuts, cinnamon, and allspice. Mix well to combine.
Add the wet ingredients: Pour in the sunflower oil and water.
Mix the batter: Stir gently with a spatula (or use a hand mixer briefly) until just combined. Do not overmix.
Bake: Divide the batter evenly between the tins. Bake for 35–40 minutes, rotating halfway through. The cakes are ready when a skewer inserted into the centre comes out clean. If needed, bake a few minutes longer. Allow to cool completely on a wire rack.
Make the icing: In a bowl, soften the vegan cream cheese with a fork. Sift in the icing sugar and whisk together until smooth and creamy.
Assemble: Place one cake layer on a serving plate. Spread half the icing over the top, leaving a small border at the edge. Place the second cake on top and gently press down. Spread the remaining icing over the top.
Decorate (optional): Finish with extra chopped walnuts, raisins, or a light sprinkle of cinnamon.
Slice and enjoy!