Some of the components can be prepared a day ahead, so all you need to do on the day is assemble and bake. It keeps well for a week, covered with cling-film at room temperature but do not refrigerate or it will become soggy.
- First prepare the syrup as this needs to be cold when poured over the hot baklava otherwise the pastry goes soggy. Combine the sugar and water and bring to the boil. Stir in honey and reduce heat and simmer uncovered, stirring occasionally for 15 minutes until it becomes denser. Add the orange blossom water, stir and simmer for a couple more minutes. Leave to cool to room temperature then refrigerate for at least 15 minutes - or overnight.
- Preheat the oven to 170°C fan.
- In a food processor, mix the pistachios, hazelnuts, pecans, orange zest and cinnamon. Pulse for about 30 seconds until it has a medium crumble consistency. Keep a handful (about 30g) of the crushed nuts on the side to decorate the top once out of the oven.
- Melt the butter and brush a thin layer over the base of a 25 x 30cm baking dish. Cut the filo to the size of your dish, leaving edges hanging over on all sides.
- Brushing each sheet with butter, lay 8 sheets of filo on the prepared dish. Spread half the nuts evenly over the pastry and cover with another 4 layers of filo pastry, brushing with butter on each layer. Add the remaining nut mixture and the last 8 sheets of filo pastry, again with melted butter between each layer and on the top.
- Using a sharp knife, cut the baklava all the way through to the bottom of the dish, into 5-6 long rows, then diagonally to make diamond shapes, about 7-8 rows.
- Bake for 50-60 minutes, until just golden and crisp. Pour half of the chilled syrup all over the top while the baklava is still warm. Wait 5 minutes then pour over the remaining syrup.
- Scatter with the remaining chopped nuts and leave to cool completely before serving.