1. Preheat your oven to 180°C/Fan 160°C/Gas 4. Grease and line 2 x 20cm cake tins with baking paper.
2. Make the cakes: peel and coarsely grate the carrots. Peel and finely grate the fresh ginger. Zest the orange. Set aside.
3. Tip the sultanas into a bowl and cover with boiling water. Leave for 5 mins then drain.
4. While the raisins soak, toast the walnuts in a dry frying pan for a few mins till darkened and nutty smelling. When cooled, roughly chop.
5. Crack the eggs into a large bowl. Add the sugar and oil and beat for 2-3 mins till light and fluffy. Use an electric mixer if you have one - it will save your arms!
6. Grate in half a nutmeg and add the other spices and salt. Mix well with a spatula.
7. Stir in the grated carrots, ginger, orange zest, sultanas, walnuts and desiccated coconut till well combined.
8. Fold in the flours and baking powder.
9. Divide the mix between the tins. Bake for 30-35 mins. The sponges should bounce back when lightly pressed. Insert a skewer into the centre of the cake. There should be no batter or crumbs on the skewer.
10. While the cakes are baking, make the cream cheese frosting. Beat the butter and icing sugar till light and fluffy. Add the lemon juice, salt and tahini and beat till combined. Add the soft cheese and beat again till well combined and cloud like. Store in the fridge. Leave to come to room temperature before decorating.
11. Now make the syrup. Squeeze the juice from the orange and half the lemon into a small pan. Add the sugar. When you are nearly ready to take the cakes out of the oven, set the pan on a medium heat and bring to the boil. Take off the heat.
12. Remove the cakes from the oven and pierce all over with a skewer. Spoon over the syrup. Leave to cool in the tins.
13. When you're ready to decorate, take your half coconut and create shavings from it using a vegetable peeler. Lightly toast them for a few mins in a dry frying pan. Toast the walnuts. Roughly chop the walnuts and crystalised ginger.
14. Dollop a little of the tahini icing in the centre of the cake plate. Place one of the cakes on top. Spoon just over half of the icing on to the cake and spread it out evenly. Top with the remaining cake. Pile the remaining icing on top and decorate generously with the toasted coconut flakes, crystalised ginger and walnuts. Dust with a little icing sugar. The cake will keep for 3-4 days in the fridge.