Pre-heat your oven to 160C Fan/180C/350F/Gas Mark, and grease and line three 8 inch sandwich tins that are at least 2 inches deep
In a large bowl, stir together both flours, baking powder, bicarbonate of soda, mixed spice and light brown sugar
In another bowl mix the vegetable oil, eggs, orange zest and juice, and ginger together using a whisk
Combine the wet and dry ingredients and whisk well
Stir in the grated vegetables and chopped pecans
Divide the mixture evenly between the cake tins, I like to use scales for accuracy
Bake for 35 minutes or until golden brown and a thin skewer inserted in the centre comes out clean. Remove them from the tins and leave them to cool on wire cooling racks
To make the buttercream, mix together the butter and icing sugar, use an electric mixer for best results
When it starts to come together add the orange extract and milk, and whisk until smooth. Then stir in the orange zest. You can add a little more milk if it's too stiff
Level the sponges if they have domed at all with a serrated knife or a cake leveller
Stack the sponges up on your plate or cake stand, piping or spreading buttercream between each layer
When you get to the last layer, pipe larger rosettes all around the edge and smaller ones in the centre
Decorate with the carrot curls, some chopped pecans and some orange zest
Serve immediately, store leftovers in an airtight container in a cool place and eat within 3 days