1Preheat the oven to 180C/160C Fan/Gas 4. Grease and line 3 deep, round cake tins – 9in, 7in and 6in.
2Put the syrup and butter in a pan and heat until melted. Stir the milk and eggs together.
3Mix the rest of the ingredients for the cake in a large mixing bowl with ½tsp salt. Add the syrup and milk mixtures and stir until smooth. Divide between the prepared tins so that each one has the same depth of cake mixture. Level the surfaces and cover the tins with foil.
4Bake the small cake for 60 mins, the medium cake for 1hr 5 mins and the large cake for 1hr 25 mins. Remove the foil from each cake 10 mins before they are due out of the oven. The cakes are cooked when they are well-risen, golden brown and a skewer inserted into the centre comes out clean. Cool on a wire rack before turning out.
5Mix together the buttercream, zest and orange extract. Trim the cakes level and slice each in 2 horizontally. Sandwich the cakes together with some of the buttercream and arrange on a 12in round cake board in a stack. Push a long skewer through all 3 cakes to secure.
6Using a serrated bread knife, carve a diagonal road shape out of the front of each cake tier. Discard the trimmings
7Spread the remaining buttercream over the cakes. Knead together 4 packs of the green ready to roll icing until soft, then roll out thinly on a surface dusted with icing sugar. Use to cover the cakes, smoothing the icing into place and cutting away any excess. Dampen the cake board with boiling water. Re-roll the green icing trimmings and use to cover the cake board.
8Whisk the egg whites until frothy, then slowly beat in the icing sugar. Continue beating until thick, glossy and stiff peaks form. Set 5tbsp of this royal icing aside and colour the remainder green.
9To make fir trees, trim the ice cream cones to 10cm in length and spread green royal icing over the outside of each one. Use a fork to form foliage, then set aside to dry.
10To make shrubs, put the marshmallows in a bowl and stir in enough green royal icing to coat the mallows completely. Divide into 8 piles set on greaseproof paper. Using more green royal icing, attach a flake to each pile and set aside to dry.
11To make rocks, add a little black food colouring to 125g of the white icing and roughly knead until grey and streaky. Use to shape small rocks. Using a little hot water, stick these to the cake along the edges of the paths. Brush the paths with honey. Crush the Oreos into crumbs and sprinkle thickly over the honey.
12To make the grass, colour 200g of the white icing green. Using a wooden spoon, push small pieces of it through a metal sieve to make shreds. Fix randomly over the cake using a little boiling water.
13To make sheep, roll out 5 marble-sized balls of white icing. Push 4 pieces of Matchmakers into each for legs. Swirl a little of the reserved white royal icing over each to create a fleece effect. Colour a little white icing black and use to shape a head and ears for each sheep. Add icing eyes and leave to dry.
14Make a gate and signposts from Matchmakers and leftover icing. Fix to the cake with the fir trees and shrubs, using leftover icing. Arrange the sheep around the cake.
