Preheat the oven to 180°C/fan 160°C/gas mark 4. Line a 36 x 24 cm baking tray with baking parchment, allowing it to extend up the sides of the tray to form a 5cm collar.
Using an electric hand mixer, whisk together the sugar and butter. Add the eggs, whisking in one at a time, and the vanilla extract. Add the flour, baking powder and a pinch of salt, and mix to combine. Stir in the nuts, white chocolate and coconut.
Spread the mixture out in the tray as evenly as possible. Bake for 10 minutes, then rotate 180 degrees and continue to bake for another 10 minutes. Be careful not to over bake. Leave in the tray to cool completely, then chill in the fridge overnight. Once completely cold, cut into bars or squares to serve.