Preheat oven to 350 degrees F. Butter the bottoms and sides of a 9 by 13-inch pan.
Mix the nuts with cinnamon, 1/4 cup sugar, and 1/4 cup of melted butter. Set aside. Unroll the phyllo pastry. Cut the whole stack in half to fit the pan. Cover the phyllo with a dampened clean kitchen towel to keep the phyllo from drying out as you work. Lay 2 phyllo sheets in the pan and using a brush, butter thoroughly. Repeat until you have 6 sheets layered. Sprinkle 1 1/2 cups nut mixture on top. Layer with 2 phyllo sheets, brush with butter and add nuts to end up with 4 layers of nuts and dough. The top layer should be about 6 to 8 phyllo sheets deep.
Using a sharp knife, cut diamond or square shapes all the way to the bottom of the pan. You may cut 4 long rows then make diagonal cuts. Bake for about 50 minutes, until the baklava is golden and crisp.
Make the sauce while the baklava is baking. Boil the water and remaining sugar until the sugar is dissolved. Add the honey and vanilla. Simmer for about 10 minutes.
Remove the baklava from the oven and immediately spoon the sauce over it. Let cool.
In the meantime, place the grapes on a baking sheet, drizzle with olive oil and remaining 2 tablespoons sugar. Bake in the oven for about 10 minutes, until the grapes start to burst.
Serve the baklava with Greek yogurt, the baked grapes and a drizzle of honey and crushed walnuts.
Cook's Notes: Walnuts can be replaced by any kind of nuts or a combination of nuts.
Phyllo pastry is available in the freezer section of most grocery stores.