Step 1: Preheat the oven to 170°C (325°F / Gas Mark 3) and grease and flour two 20cm (8-inch) round cake tins — this prevents sticking and ensures even baking.
Step 2: Sift together flour, bicarbonate of soda, cinnamon, nutmeg, and ginger in a large bowl — this ensures even distribution of spices and removes lumps.
Step 3: In a separate bowl, whisk together sugar, eggs, and oil — this creates a smooth, emulsified base for the batter.
Step 4: Gradually mix the wet ingredients into the dry ingredients — stir until just combined to avoid overmixing, which can cause a tough texture.
Step 5: Fold in grated carrots, chopped walnuts, and raisins — mix until evenly distributed throughout the batter.
Step 6: Divide the batter evenly between the tins and bake for 30–35 minutes, or until a skewer inserted in the center comes out clean.
Step 7: Let the cakes cool in the tins for 10 minutes, then transfer to a wire rack to cool completely.
Step 8: Make the frosting by beating together cream cheese, butter, and vanilla extract until smooth. Gradually add icing sugar and beat until light and fluffy, with no lumps.
Step 9: Once cakes are fully cooled, spread a layer of frosting on one cake, place the second layer on top, then frost the top and sides. Garnish with extra walnuts if desired.