The first thing you want to do is thaw the phyllo dough overnight. You want to give it enough time to come slowly come down to a warmer temperature before working on it. If you try to use it right away, the phyllo dough will break apart.
Then place the thawed phyllo dough onto your countertop and let it sit at room temperature for about 1 hour. This step st also very important. Don't try to rush it.
While you wait for the phyllo dough, start making the honey syrup. In a saucepan, add 3/4 cup granulated sugar, 1 cup water, 1 cup honey, and 3 tablespoons fresh lemon juice. Place the saucepan on the stove and bring the mixture to a boil making sure to stir constantly. Then let it simmer in the saucepan at medium-low heat for about 8-10 minutes undisturbed. Then set it aside to cool. Place 3 heaping cups shelled lightly salted pistachios and 1/2 tsp cinnamon into a food processor. Pulse the food processor at high speed until the pistachios are crushed down to a fine crumb. Then set it aside.
Now trim the entire stack of phyllo sheets (at least 35 sheets) so that they fit a 9x13 inch baking dish. I just slice the edges off with a sharp knife. Then quickly cover the phyllo sheets with a thin damp towel to keep them from drying out.
Melt 1 cup of unsalted butter in a saucepan then use a pastry brush to brush the butter onto the bottom of the baking dish.
Now place a sheet of phyllo dough into the pan. Then brush with butter again, and repeat this process with another 4 sheets of buttered phyllo dough (so a total of 5 sheets with butter in between each sheet).
Now sprinkle 1/2 cup of the chopped pistachios on top of the phyllo sheet.
Then repeat this same process again. So another 5 buttered sheets, then 1/2 cup of pistachios. You will need to do this process a total of 6 times. Then after you’ve placed the last 1/2 cup of nuts, finish it off with 5 more buttered phyllo sheets. Make sure the top layer had a generous amount of butter brushed on top. Tip: If your butter starts to stiffen, just reheat it on the stove for a few minutes on low heat. Also, If you ever get confused, see the notes section for the detailed order of assembling baklava.
To cut the pastry, make 3 even slices lengthwise so you have a total of 4 (1 1/2 inch) wide strips. Then cut diagonally so that each piece of baklava is in the shape of a diamond.
Now bake the pistachio baklava at 350 degrees Fahrenheit for 40-50 minutes.
As soon as you pull the baklava out of the oven, immediately pour the honey syrup over the entire pastry. The hissing bubbly sound will be quite satisfying to hear! 😉
Now let the baklava sit for a few hours before serving. But it tastes even better the next day. So you can totally make this a day in advance!