Place the phyllo dough in the refrigerator overnight.

Remove the phyllo dough from the refrigerator 1 hour before starting the recipe.

Let the phyllo dough come to room temperature on the counter.

If your baking dish is 13x9 inches, trim the phyllo dough slightly so that it fits snugly.

Keep the remaining phyllo dough covered with a damp towel to prevent it from drying out.

Butter the bottom and sides of a 13x9 inch non-stick baking pan.

In a medium saucepan, combine the sugar, honey, lemon juice, and water.

Bring the mixture to a boil over medium-high heat, stirring until the sugar is dissolved.

Reduce the heat to medium-low and simmer for 4 minutes without stirring.

Remove the saucepan from the heat and let the syrup cool.

Preheat the oven to 325 degrees Fahrenheit (165 degrees Celsius).

Pulse the walnuts in a food processor until they are coarsely ground.

In a medium bowl, stir together the walnuts and cinnamon.

Place 10 sheets of phyllo dough in the prepared baking pan, brushing each sheet with butter before adding the next.

Spread 1/5 of the nut mixture (about 3/4 cup) over the phyllo dough.

Add 5 buttered sheets of phyllo dough.

Spread another layer of nuts over the phyllo dough.

Repeat this process 4 more times.

Finish with 10 layers of buttered phyllo dough.

Brush the very top with butter.

Use a sharp knife to cut the baklava into 1 1/2-inch wide strips.

Cut diagonally to form diamond shapes.

Bake the baklava for 1 hour and 15 minutes, or until the tops are golden brown.

Immediately spoon the cooled honey sauce evenly over the hot baklava.

Let the baklava cool completely, uncovered, at room temperature.

For best results, let the baklava sit for 4-6 hours, or overnight so that the syrup can penetrate and soften the layers.

Garnish with chopped nuts or melted chocolate, if desired.

Serve at room temperature.