Place the sugar and water in a saucepan and heat the stove top, stirring occasionally, until the sugar dissolves. Add the honey and whole cloves; stir to mix. Bring to a boil. Lower heat and let simmer for about 25 minutes.
Remove syrup from heat and let cool to lukewarm.
Add lemon juice. Remove the whole cloves.
In the bowl of a food processor fitted with a blade, add the pistachios, walnut, and hazelnuts. Pulse a few times to chop. Transfer to a large mixing bowl and add sugar, cinnamon, and ground cloves. Mix well to combine.
Unroll the thawed phyllo pastry and place the sheets in between two clean kitchen towels. This will help keep the phyllo from breaking while you work.
Assemble the baklava:
Brush the interior of a 9”x 13”x 2” baking pan with some of the melted butter.
Take one sheet of phyllo and place it in the pan. Fold or trim as needed to fit the pan. Brush the top of the phyllo sheet with the melted butter. Repeat this process a few more times until you have used up about ⅓ of the phyllo pastry, each layer being brushed with the melted butter. Distribute about ½ of the nut mixture evenly over the top layer of phyllo.
Continue assembling the baklava, one sheet of phyllo pastry at a time, using another ⅓ of the phyllo. Again, brush each layer with a bit of melted butter. Distribute the remaining ½ of the nut mixture evenly over the top layer of phyllo.
Finish the remaining ⅓ of the phyllo pastry following the same process, laying one folded sheet at a time and brushing each layer with melted butter. Brush the very top sheet of phyllo with butter.
Using a sharp knife, cut the pastry into 24 diamond-shaped pieces.
Place the baking dish on the middle rack of your heated oven. Check the baklava halfway through baking. Bake anywhere from 35–45 minutes or until the top of the baklava turns golden and a skewer inserted in the center comes out clean.
As soon as the baklava is removed from the oven, pour the cooled syrup all over the hot baklava.
Allow baklava to sit for a few hours before serving or for at least 1 hour.
Cut through the earlier marked pieces. Serve with a garnish of chopped pistachios, if you like.