Start by getting everything ready. Heat the oven to 180°C (160°C if using a fan oven). Take a round cake tin, lightly grease it with oil, and line the base with baking paper so the cake doesn’t stick.
Crack the eggs into a large bowl and add the sugar. Whisk them together until they are well mixed. Slowly pour in the vegetable oil while whisking, and keep going until the mixture looks smooth and slightly glossy.
Next, add the yogurt and vanilla extract. Tip in the grated carrots and the sultanas or raisins. Stir gently so everything is evenly mixed, but don’t beat it too hard.
In another bowl, mix together the flour, cinnamon, and grated nutmeg. Add this dry mixture to the wet ingredients and fold it in carefully, just until combined. Try not to overmix, as this can make the cake heavy.
Fold in the chopped walnuts. At this stage, the batter should be thick but still easy to pour.
Pour the batter into the prepared cake tin and smooth the top. Place it in the oven and bake for about 50 to 55 minutes. The cake is ready when a skewer pushed into the centre comes out clean.
Once baked, remove the tin from the oven and let the cake rest in it for about 10 minutes. Then turn it out onto a cooling rack and leave it to cool completely before adding the frosting.
To make the frosting, beat the butter and caster sugar together until light and creamy. Add the cream cheese and mix gently until smooth. Once the cake has fully cooled, spread the frosting evenly over the top.