For the carrot decorations, colour the icing with orange colouring, to your preferred shade, you may need a little icing sugar if it gets too sticky. Divide the icing into 9 equal pieces and shape into carrots. Colour the remaining icing green to your preferred shade and make the carrot tops.
Preheat the oven to 180C/Fan160/Gas Mark 4. Grease and line the base and sides of 2 x 21cmx11cm (900g) loaf pans with baking parchment.
Place the butter and sugar in a large mixing bowl. Beat with an electric hand held beater until light and fluffy. Slowly add the eggs beating well between each addition. Fold in the flour, baking powder, using a large metal spoon.
Spoon 1/2 of the batter into a large mixing bowl. Add the carrot and almonds and stir to combine. Add orange colouring to your colour liking.
Add the desiccated coconut, juice and lime zest to the bowl and stir to combine.
Spoon the carrot batter into one of the loaf pans and the coconut and lime batter in the other loaf pan. Smooth the surfaces and bake in the centre of the oven for 40 minutes or until just firm to touch. Allow to cool on a cooling rack before removing the tin and paper.
Warm the jam in a pan with 1 tbsp water. Place both cakes side by side on a chopping board. If the tops are uneven use a sharp serrated knife to slice off the tops so they are of an even height. Cut both cakes down the centre lengthways into 4 even slices.
Brush 1 of the carrot slices with the jam. Place one of the coconut and lime slices next to it and brush with jam. Stack with the final 2 slices in a checkerboard pattern. Securing the slices with the jam. Brush the top of the cake with jam.
Dust a work surface with icing sugar. Roll out the icing the length of the cake and long enough to wrap around the sides.
Brush the icing with jam. Place the cake upside down in the centre of the icing and wrap the icing around it. Press the icing firmly together to seal. Trim any excess icing. Turn the cake over so the join is on the base. Trim the icing at the ends of the cake. Place the cake on a serving plate. Decorate the cake with the carrots. Sprinkle with toasted coconut, if using.