Preheat the oven to 220ºC, fan 200ºC, gas 6. Melt the butter with 225ml water in a large saucepan. As soon as the liquid has come to a rolling boil, tip in the flour and remove the pan from the heat.
Using a wooden spoon, beat vigorously until the mixture comes together to make a thick paste. Leave to cool for at least 10 minutes.
Gradually beat in the eggs until the mixture is glossy, smooth and has a dropping consistency. Spoon into a piping bag fitted with a medium star nozzle.
Pipe 20x5cm lengths, leaving space in between, on to 2 non-stick baking sheets. Pipe rounds of paste with any extra mixture .
Bake for 12 minutes. Reduce the heat to 200ºC, fan 180ºC, gas 6, bake for a further 10 minutes. Remove from the oven, pierce a hole in each eclair to release the steam and cool them on a wire rack before arranging in the shape of a Christmas tree.
In a bowl, mix together the cream, sugar and brandy. Spoon into a piping bag fitted with a small plain nozzle. Pipe the cream into each eclair. Dip the eclairs in the melted chocolate and chill until ready to serve.