Preheat your oven to 180 deg C and line a baking tray with baking paper.
Combine the walnuts, cashews, orange zest, cinnamon, cardamom and dark chocolate in a food processor and process the mixture till it becomes coarsely chopped (do not over mix to make it look like meal). Set aside.
Take a sheet of fillo and lay it on a clean bench with the longer edge facing you and brush liberally with butter. Repeat with 3 more sheets and stack neatly on top of one another (you will need 4 sheets total).
Leaving a 5cm border, spoon 5-6 tablespoons of the baklava filling in a single line across the longer edge. Roll the fillo tightly to form one long piece and cut into 8 portions. Repeat with the remainder of the fillo and filling until you have 24 pieces.
Brush with butter and bake for 20-25 mins or until golden brown.
Start the sugar syrup 10 mins before taking out the cooked baklava rolls. Combine the sugar, water, honey and juice in a saucepan on a medium high heat. Allow the mixture to come to a rapid boil and then lower the heat and simmer till you have a thick syrup. Spoon over the baklava whilst hot from the oven.
Serve as a snack or with coffee.