For the brownie batter melt the butter and chocolate squares in a large microwave safe bowl for 2 minutes, stirring every 30 seconds, until completely melted. Let cool slightly before stirring in the sugar. Beat in the eggs and vanilla until well combined. Stir in the flour and cinnamon. Fold in 1-½ cups chopped walnuts. Set brownie batter aside.
Roll fillo dough out onto a work surface. Place a 9x13-inch baking dish in the center of the fillo and cut around the edges with a sharp knife so that the fillo sheets are shaped to fit the dish. Cover the fillo with a damp cloth while you are assembling the baklava.
Melt 1 cup butter in a microwave safe bowl. Spread the bottom and sides of the 9x13-inch baking dish with some of the melted butter. Place a sheet of fillo in the bottom of the baking dish and brush generously with the melted butter. Repeat with 6 more sheets of fillo dough, brushing each sheet with melted butter..
Spread half of the brownie batter evenly over the 7 sheets of fillo that are in the bottom of the baking dish. Layer 6 more sheets of fillo dough, brushing each sheet generously with melted butter, on top of the brownie layer. Spread the remaining brownie batter over the middle layers of fillo dough.
Top the second layer of brownie batter with the remaining phyllo sheets, brushing each sheet with melted butter. Using a sharp knife, cut the unbaked baklava into 24 squares. Brush with remaining butter and sprinkle with remaining ½ cup chopped walnuts.
Bake for 30-35 minutes or until baklava is golden and starting to crisp on top. Remove from the oven and drizzle with 1 cup honey. Let baklava set for 3 hours then drizzle with remaining ½ cup honey before cutting and serving