Preheat the oven to 180C/350F. Slice your phyllo dough in half, and set 145 sheets aside, for the top and bottom of the baklava. Cover them in a damp kitchen towel, to avoid them drying out.
In a mixing bowl, combine your chopped walnuts with cinnamon and set aside. Brush a 9 x 13-inch baking dish with butter.
Place two sheets of the phyllo dough into the bottom of the buttered dish. Brush with more butter. Repeat this process three more times, so you are left with 8 sheets with phyllo dough. Sprinkle two heaped tablespoons of the chopped nuts on top, followed by two sheets of dough, and brush with butter. Repeat this process, until the remaining 6 sheets are left. Place those on top. Using a sharp knife, cut diamond shapes, leaving an inch from the bottom of the dish.
Bake the baklava for around 45 minutes, until golden on top.
While the baklava is baking, prepare the sugar syrup. In a small saucepan, combine your sugar and water. On medium heat, bring to a boil. Once it's boiling, remove from the heat and add in the maple syrup and extract. Place back on the heat and on low heat, let it simmer for 20 minutes.
Once the baklava is baked, pour the sugar syrup to cover it completely. Let it cool completely, beforeusing the knife again to cut to the very bottom of the baking dish, for the syrup to seep through. Top with crushed nuts and serve.
* For gluten free baklava, use gluten free phyllo dough.** You can also use chopped pistachios or a combination of the two. *** If you aren't strictly vegan, you can use honey. TO STORE: Leftover baklava can be stored in the refrigerator for up to 1 week. DO NOT cover it up, otherwise, it will become soggy. TO FREEZE: Place baklava is a freezer friendly container and store in the freezer for up to 6 months. Thaw in the refrigerator uncovered.