1Preheat the oven to 180C/160C Fan/Gas 4. Grease and line a 20cm-square deep brownie tin.
2Break up the chocolate into a heatproof bowl. Add the butter and dark brown sugar, then place over a saucepan of barely simmering water until melted. Don’t allow the base of the bowl to touch the water. Carefully take the bowl off the pan, stir the mixture well to combine, then allow to cool for 10 mins.
3Mix in the eggs and vanilla extract to make a thick, glossy mixture. Add the fruit and brandy or rum (or fruit juices, if using), then sift the flour and baking powder on top. Mix together thoroughly to make a thick cake mixture.
4Spoon into the prepared tin, smooth the top and bake for about 17-20 mins until risen – the brownie should be slightly soft with a bit of a crust on top. Allow to cool in the tin.
5Wrap the cooled brownie and the tin in baking paper and foil, then store in a cool, dark place for 24 hrs to allow the texture and flavour to develop.
6To decorate, turn the brownie out of the tin and discard the baking paper. Place upside down on a board and brush the top with honey. Set aside.
7Gently knead the marzipan to soften. Lightly dust the work surface with icing sugar, then roll out the marzipan into a square to fit the top of the brownie. Gently press in place and trim off any excess as necessary.
8Using a large, sharp knife, divide the brownie evenly into 3 large bars. Brush the marzipan with a small amount of water to make it sticky.
9Working one colour at a time, roll out the white, red and green icing – each should form a strip about 1cm longer and wider than 1 of the brownie bars. Trim off any rough edges, gently press 1 colour on each of the bars, then carefully trim away any excess. For the best finish, dust your fingertips with icing sugar, then rub the top of the icing until smooth.
10When all 3 bars are iced, cut each one into 4 equal pieces – this is a crumbly cake so use a large, sharp knife to get a neater edge.
11Roll out the yellow icing, then gather up and roll out any icing offcuts, keeping the colours separate. Using mini cookie cutters (or a sharp knife), stamp or cut out festive shapes, such as Christmas trees, holly leaves, stars and snowflakes. Decorate each brownie, using a little water to stick the shapes on top. For an extra flourish, add texture to the edges of the icing with a serrated tool or knife.
12Your brownies are now ready to serve and enjoy!