1. Heat the oven to 180C/350F/Gas Mark 4.
2. Make the syrup. Place a syrup pan or heavy saucepan over a low-medium heat and add the honey, sugar, orange zest, cinnamon stick and water. Bring to the boil and simmer for 10 minutes or until the syrup lightly coats the back of a metal spoon. Remove from the heat and set aside to cool slightly. Add the lemon juice and the orange flower water, if using.
3. Make the filling. In a small bowl, combine the walnuts, almonds, honey, cinnamon and cloves.
4. Brush a 23x30 cm baking pan or cake pan, with sides at least 6cm deep, with melted butter (or choose a pan that fits the size of your filo sheets). Arrange one filo sheet in the pan, and brush with a little butter; repeat with two more sheets. Divide the filling into four portions. Very lightly, spread one portion over the filo (avoid pressing down on the pastry). Cover with one filo sheet, brush with melted butter and place another sheet on top. Brush this with butter, spread a second portion of filling over it, and repeat until filling and filo are used (ending with filo). Liberally brush with butter. With a small, sharp knife, carefully cut through (score) the top two filo sheets to make squares or diamond shapes.
5. Bake for 40 minutes or until the top is golden brown. Immediately after you remove the baklavas from the oven, use a sharp knife to cut into the shapes you have scored; cut through to the bottom of the pan. Strain over the syrup and discard the cinnamon stick and orange zest. Cover the pan with a clean tea towel and set aside for at least four hours.