• Preheat the oven to 170°C. Grease and line the base of either 1x 18cm (7in) springform cake tin or 2x 18cm (7in) sandwich cake tins.
• In a large mixing bowl, whisk one whole egg, 2 egg yolks, sugar and sourdough starter together. Set the remaining two egg whites aside.
• Little by little add the oil, and keep whisking until it's fully incorporated.
• In a separate bowl, combine flour, baking soda, baking powder, salt, cinnamon and mixed spice.
• Add the dry ingredients to the wet ingredients and mix just enough to combine.
• Add the grated carrots, pecans, coconut and sultanas and mix again to incorporate.
• In a separate bowl, whisk reserved egg whites to stiff peaks.
• Mix the egg whites gently, ⅓ at a time, attempting to keep some of the air in the mixture.
• Spoon the mixture into the prepared cake tin (or divide it between two sandwich cake tins), and place in the preheated oven - 30 minutes for sandwich sponge tins, and about 50-55 minutes for one cake.
• Once baked, a wooden skewer insterted into the middle should come out clean.
• Leave the cakes to cool down and firm up in the tins for 15-20 minutes, then run a blunt knife around the edge of the tin, and turn the cakes out onto a wire rack to cool down completely.

Frosting

• When your carrot cake has cooled down to room temperature, prepare the frosting.
• In a bowl or a large jug, beat the softened butter, icing sugar and honey using an electric handheld mixer until very light and fluffy.
• Add ⅓ of cream cheese and beat again until smooth and well combined. Scrape the sides of the bowl to ensure no butter is clinging to the sides.
• Add the rest of the cream cheese and beat again until you have a smooth creamy frosting. If it's not holding shape, a short chill time will help with consistency before spreading.
• If you baked one tall cake, cut it in two. You may choose to spread half of the cream cheese frosting in the middle and half on top, or go for an all-over approach.