1. Preheat your oven to 180°C/Fan 160°C/Gas 4. Fill and boil your kettle. Grease 2 x 20cm cake tins with a little sunflower oil, then line them with baking paper.
2. Start by making the cakes. Peel and coarsely grate the carrots. Peel and finely grate the fresh ginger. Finely grate the zest from 1 orange. Tip the sultanas into a bowl and cover with boiling water. Leave for 5 mins then drain. Set to one side.
3. While the sultanas soak, toast the walnuts in a dry frying pan for a few mins till darkened and nutty smelling. Tip onto a board and let them cool for a few mins, then roughly chop them.
4. Crack the eggs into a large bowl. Add the sugar and sunflower oil and beat for 2-3 mins till light and frothy. Use an electric mixer if you have one – it will save your arms! Grate in half a nutmeg then add the ginger, cinnamon and 1 tsp sea salt. Mix well with a flexible spatula.
5. Stir in the grated carrots, ginger, orange zest, sultanas, walnuts and desiccated coconut till well combined. Fold in the flours and baking powder.
6. Divide the mix between the tins. Bake for 30-35 mins till golden and risen. The sponges should bounce back when lightly pressed. To check if they're baked, insert a skewer into the centre of the cake. There should be no batter or crumbs on the skewer.
7. While the cakes are baking, make the cream cheese frosting and syrup. To make the frosting, beat the butter and icing sugar together till light and fluffy. Add the lemon juice, a pinch of salt and the 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.
8. Now make the syrup. Squeeze the juice from 1 orange and half a lemon into a small pan. Add 60g sugar and set the pan on a medium heat and bring to the boil. Once it has started boiling, take the pan off the heat.
9. Remove the cakes from the oven and pierce all over with a skewer. Spoon over the syrup. Leave to cool in the tins.
10. When you're ready to decorate the cakes, crack open a coconut, drain away the coconut water (save it to drink it) and peel shavings off half the coconut with a vegetable peeler. Lightly toast the coconut shavings in a dry frying pan for a few mins till golden. Tip into a bowl. Add 50g walnut halves to the hot frying pan and toast for a few mins till nutty. Tip the walnuts onto a chopping board, let them cool for a few mins then roughly chop them. Roughly chop the crystalised ginger.
11. Dollop a tablespoon of the tahini icing in the centre of a serving 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 with the toasted coconut flakes, crystalised ginger and walnuts. Dust with a little icing sugar. Serve in slices.
12. Eat Me, Keep Me
The cake will keep for 3-4 days in the fridge.