1. Preheat the oven to 350°. Spread the nuts on a baking sheet and bake for 12 minutes, until the skins are blistered; let cool. Leave the oven on. Transfer the nuts to a kitchen towel and rub off the skins, then transfer to a food processor and pulse until coarsely chopped.
2. Add the chocolate, 2/3 cup of the sugar and the cinnamon to the food processor and pulse until the chocolate and nuts are finely chopped and the same size.
3. Unwrap the phyllo and cover with a sheet of plastic wrap. Generously butter a 9-by-13-inch metal baking pan. Butter and stack 8 sheets of phyllo. Trim the edges. Ease the stack into the pan. Sprinkle about 2 cups of the filling over the phyllo. Butter and stack 2 more phyllo sheets; fold them in half crosswise and place over the filling. Sprinkle on another 2 cups of the filling. Top with 2 more buttered, folded sheets and 2 cups of filling. Butter and stack 3 more phyllo sheets, fold them in half and place over the filling. Fold in the overhanging phyllo on top and brush generously with butter. Using a ruler and a sharp knife, cut the baklava (through the top and bottom) into 3-inch squares (there will be a bit left on one long side). Cut each square in half to make triangles.
4. Bake the baklava for 25 minutes, then lower the oven temperature to 300° and bake for 50 minutes longer, until golden.
5. In a saucepan, bring the water, honey and the remaining 2 cups of sugar to a boil. Simmer over moderate heat for 10 minutes. Immediately ladle the hot syrup over the hot baklava and let stand until completely cool, at least 4 hours and preferably overnight.