Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and grease and line two 8 inch sandwich tins (that are at least 2" deep)
In a large bowl, stir together the self raising flour, wholemeal flour, baking powder, bicarbonate of soda, mixed spice, cinnamon and light brown sugar
In another bowl or large jug, whisk together the vegetable oil, eggs, orange zest and orange juice. Then add it to the flour mixture and whisk everything together
Mix in the grated carrot, chopped pecans and sultanas
Divide the mixture evenly between the cake tins, use scales for accuracy
Bake for 40-45 minutes until golden brown and a thin skewer inserted in the centre comes out clean. Remove them from the tin and leave them to cool on wire racks
If the cakes have domed on top, level them off with a cake leveller or a knife
To make the frosting, use an electric mixer to beat the butter on it's own until soft and creamy
Add the icing sugar, and mix in until well combined
Add the cream cheese and the vanilla extract, mix until just combined and smooth
Place one of the sponges onto a plate or cake stand and spread or pipe some of the frosting over it
Top with the second sponge, then pipe or spread the remaining frosting on top
Decorate with fondant carrots and chopped pecans
Store any leftovers in the fridge for up to 3 days
Video
Notes
Make sure all your ingredients (particularly the butter and eggs) are at room temperature before you start baking.
I used a baking spread for the cake and unsalted butter for the buttercream.
If you don't have wholemeal plain flour, you can use regular plain flour, or the same amount of self raising flour and omit the baking powder.
Mixed spice is a British spice blend containing cinnamon, coriander seed, nutmeg, clove, pimento, and ground ginger. If you can't get hold of it where you're based, you can use a Pumpkin Spice mix instead or add a mix of cinnamon, ginger, nutmeg and ground cloves.
You can swap the pecans out for the same amount of walnuts, or you can leave them out altogether if you want the cake nut free.
I like to use sultanas as they are more juicy, but you can swap them out for raisins, or again leave them out if you prefer.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.