Ingredients

Step by step

1. Preheat the oven to 180°C, fan 160°C, gas 4. Grease and line a 23cm x 33cm baking tin.
2. Add the butter, dark chocolate and both sugars to a large non-stick pan. Heat gently, stirring; you want the chocolate to melt and everything to be liquid but not hot. Pour into the bowl of a stand mixer, then, using the paddle beater attachment, gradually mix in the milk and vanilla on slow speed.
3. In another large bowl, dry whisk the plain flour, cocoa and salt together to evenly mix the powders, then fold this into the chocolate mixture in batches, on slow speed.
4. Fold in the white chocolate chips on slow, then pour the batter into the prepared tin. Cook for about 30 minutes until just baked; it should be set around the edge but slightly underbaked and fudgy in the middle. A knife should come out with some paste-like mixture on it, not glistening but not dry, and it should still have a nice wobble. Remember it will firm up as it cools. Leave to cool in the tin.
5. For the white chocolate buttercream, gently melt the chocolate until smooth and lump-free. Set aside to cool slightly.
6. Beat the butter and vanilla until very pale and creamy, then add half the icing sugar, beating slowly until incorporated, then turn up the speed and beat until light and fluffy. Repeat with the rest of the icing sugar.
7. Add the cooled melted white chocolate and beat in well until fully incorporated, light and fluffy. Finally, add in 1-2 tablespoons of milk to loosen; you want it to still be able to hold its shape but be soft and spreadable. Load into a large piping bag fitted with a 1cm round nozzle, or cut a hole about 1cm across if using a disposable bag.
8. Carefully turn out the brownie traybake and cut out a triangular tree shape from the centre top to both bottom corners. The two triangles that remain can be used to make a second Christmas tree, or cut into wedges to eat separately. Transfer to a serving board and add the white chocolate bar as the trunk.
9. To decorate, pipe the buttercream as shown over the tree shape; start with one blob at the top of the tree, then go around the outside in a neat line before filling in the middle. Adorn with mixed gold, white and silver sprinkles to create metallic garlands to bring the tree to life, add a few coloured sprinkles as ‘lights’, then dot the gold pearl balls around as baubles, with one at the top of the tree.