Using a food processor, finely chop the walnuts.
In a medium bowl, stir together the walnuts and cinnamon.
Place 10 filo sheets into baking pan one at a time, brushing each sheet with butter once it's in the pan before adding the next. Keep covered with a damp towel at all times.
Spread about 3/4 cup of nut mixture over filo
Add 5 buttered sheets of filo, then another layer of nuts. Repeat x 4. Finish off with 10 layers of buttered filo sheets. Brush top with butter.
Cut pastry to form diamond shapes. Bake at 165 degrees for 1 hour and 15 min or until golden brown.
Remove from oven and immediately spoon cooled syrup evenly over the hot baklava. This will ensure that it stays crisp rather than soggy. Let baklava cool completely, uncovered and at room temperature.
Garnish baklava with leftover walnuts and drizzle with melted chocolate.