Method:

Preheat the oven to 180C prepare two baking sheets.
Place the water, butter and sugar in a saucepan and heat up until the sugar and butter have completely melted. Remove the saucepan from the heat and add in the flour. Stir the batter with a wooden spoon until it starts to come together then place back on the stove on a low heat. Cook and stir until a thin film form at the base of the saucepan. Transfer the batter into a large bowl and cool until almost at room temperature but still warm. Using a whisk, whisk in one egg at a time. Completely mixing with each addition. Transfer the batter into a large piping bag fitted with a round nozzle. Pipe small mounds if pastry leaving space between each choux as they will puff in the oven. Bake for 20 minutes or until puffed and golden. Then open the oven door to let the steam out and reclose it and bake for a further 10 minutes. Remove from the oven and cool. In a large bowl, melt the chocolate tips and half the cream. In a separate bowl, beat the remaining cream with the icing sugar and vanilla and icing sugar until stiff peaks. Fold the cream into the melted chocolate mixture gently. Transfer into a piping bag and place in the fridge for 10 minutes. Prepare your decorating ingredients, by adding a few drops of green food colouring into the white chocolate. Make a whole at the base of each bun, pipe the mousse into each bun until full then dip the buns into the green chocolate. Arrange the choux buns on a cake stand in the shape of a cone. Carefully place sweets on the tree and dust with icing sugar to finish off.