This carrot and walnut cake is the perfect woodland-themed celebration cake. Let your imagination go wild and decorate with as many flowers, leaves and fairies as you like.
Make the large sponge and hemisphere mixture. Preheat oven to 180°C/160°C fan/Gas 4. Put the sultanas in a bowl with the orange juice and zest and microwave for 2 minutes until plumped up.
Put the sultana mixture in a large (6-litre) bowl and add all the remaining large cake ingredients. Using a large metal spoon, combine to a thick batter, then spoon the mixture into the hemisphere mould until three quarters full and divide the remainder equally between the two 25cm cake tins. Bake the hemisphere for 45 minutes, and the large cakes for 1 hour–1 hour 5 minutes, or until a skewer inserted into the centres comes out clean. Leave to cool in the tins for 15 minutes, then turn out onto a wire rack to cool completely.
Repeat steps 1 and 2 for the smaller sponge mixture, dividing the mixture equally between the two 15cm cake tins and baking for 50–55 minutes, or until a skewer inserted into the centres comes out clean. Leave to cool as before.
Make the icing. Beat the butter in the bowl of a stand mixer fitted with the beater until soft and creamy. Add the cream cheese and beat again on a low speed until just combined. With the mixer still on low, add the icing sugar in two batches, beating gently between each addition, then add the orange zest and the cinnamon to taste. Refrigerate until needed.
When all the sponges have cooled, sandwich the two 15cm sponges with a little cream-cheese icing. Trim and carve the stacked cake to make it slightly narrower at the top to resemble a toadstool stem. Place on one of the 15cm cake cards, then spread the whole cake thinly with icing to create a crumb coat.
Begin the decoration. Knead 600g of the sugar paste with ivory food colouring to the desired shade. Roll it out on a work surface dusted with icing sugar to a rectangle about 45 x 10cm. Wrap the icing around the cake, overlapping it on the top. Push three lengths of dowelling in a triangle formation into the centre of the cake. Trim to length. Set aside.
Place the hemisphere cake on the second 15cm cake card, attaching it with a small dab of cream-cheese icing. Spread the hemisphere with a thin layer of cream-cheese icing and chill for 10 minutes.
Roll out 250g of the remaining sugar paste to a circle large enough to cover the cake. Drape this over the chilled hemisphere and trim the edge to neaten. Mix a little red food colouring with a drop of the alcohol and, using the cake-decorating paintbrush, paint red all over the iced hemisphere to make the toadstool cap. Position on top of the toadstool stem.
Roll out a little more of the white sugar paste (re-roll the cap trimmings, too) and, using the 3cm cookie cutter, cut out six 3cm white circles. Arrange on the top of the toadstool cap. Colour about 75g of the remaining sugar paste pink. Roll it out and use it to cut out a door (add detail using the blunt side of the knife) and little blossom flowers. Press the door onto the cake (use a little remaining cream-cheese icing to attach, if necessary).
Colour half the remaining sugar paste green, roll it out and, using the cutters, cut out leaf shapes. Colour most of the remaining icing brown and shape acorns, saving a little to colour red to make a few darker flowers. Set aside on baking paper.
Colour the remaining cream-cheese icing with light brown food colouring to reach the desired shade. Sandwich the two 25cm cakes with a little buttercream, then place them on the 30cm cake drum. Place the remaining three cake dowels in a triangle formation in the centre of the cake, then trim to length.
Spread the remaining brown icing over the top and sides of the large cake. Using a palette knife, add texture to the icing to resemble bark.
Using edible glue, stick all the flowers, leaves and acorns all over the cake to decorate. Mix the desiccated coconut with green food colouring to resemble grass and sprinkle this around the base of the cake and base of the toadstool to finish.