1.Grease four oven trays; line each with baking paper. Mark nine crosses, measuring 7cm, 9cm, 11cm, 13cm, 14cm, 15cm, 16cm, 17cm and 18cm on trays, leaving about 3cm space between each cross. Mark an 18cm cross on cake board.
2.Combine chocolate and hazelnuts in medium bowl. Drop teaspoonfuls of the chocolate mixture along all the marked crosses to make branches; refrigerate several hours or overnight.
3.Drop about a teaspoon of the extra melted chocolate into the centre of the 18cm cross on cake board; position the 18cm branch on top, moving it around until the best position is found.
4.Assemble the remaining eight branches in pairs, starting from the largest remaining branch and finishing with the smallest, using about a teaspoon of the extra melted chocolate in the centre of each crossed pair; refrigerate until set.
5.Secure each pair to the next with a little melted chocolate (if the branches look a little uneven, support them underneath with a match box). Secure brazil nut to centre of smallest branch with a little melted chocolate; drizzle remaining melted chocolate over nut to cover it in chocolate. Refrigerate until chocolate sets between branches. Store tree in refrigerator until required; dust with sifted icing sugar.
This tree takes a little time to make, but it is delightful to look at and delicious to eat. The Christmas tree can be made two days ahead. Bring out this tree with the coffee, suggesting to your guests that they snap off bits of the branches. Or, for an impressive gift, wrap the whole tree in cellophane and deliver it on the day.