You will also need a 20cm (8”) spring form cake tin, greased and the base lined with parchment paper, plus a piece to cover the cake and some for the caramelised walnuts.
Preheat the oven to 170°C/Fan 150°C/325°F, Gas Mark 3.
把油倒进碗厄尔ectric mixer, add the sugar and beat briefly until combined on a medium speed. Reduce the speed down to low, add the egg and the yolk, followed by the carrots, walnuts, coconut and orange zest.
Sift together the flour, baking powder, bicarbonate of soda and cinnamon, add to the mixing bowl and briefly mix in just enough to combine, scraping down the sides. Tip into a large bowl, then wash up the mixer bowl, ensuring it is completely dry and clean. Add the whites and salt and whisk until firm peaks form. Using a large metal spoon, carefully and lightly fold in 1 spoonful of the egg white into the cake mixture to loosen it then add the rest.
Pour the mixture into the cake tin and bake on the middle shelf of the oven for 55-65 minutes until golden and risen and a fine skewer comes out clean when inserted into the middle. Cover the cake with the parchment paper after 40 minutes to stop it from overbrowning – no sooner or the paper will stick to the top. Leave the cake to cool completely in its tin then turn out onto a wire rack and peel off the paper. Cut in half.
Next, make the icing by beating half the cream cheese, all the butter, sugar, orange zest, and orange and lemon juice together in a bowl until smooth. Add the rest of the cream cheese and beat again until light and fluffy. Sandwich the cakes together with a little of the icing, then cover the top and sides of the cake with the rest and decorate with the walnuts. Lift onto a plate and serve.