This dessert just gets better with time. I would always plan on serving it the next day, or even the day after that, as the longer it sits, the longer the matzo has a chance to soak up the sweet lemony syrup. This recipe will make 9 to 16 squares (depends how small you slice it).
6 sheets matzo
1 cup water
2 cups sugar
3 tablespoons fresh lemon juice
1 tablespoon honey
1 cup walnuts, chopped
1 cup shelled raw unsalted natural pistachios, chopped
1 cup packed brown sugar
½ teaspoon ground cinnamon
½ teaspoon ground cardamom
½ cup (1 stick) unsalted margarine or butter, melted
Briefly pass each sheet of matzo under cold running water until wet on all sides. Layer sheets between damp paper towels and let stand until somewhat pliable but not soggy or falling apart, about 2 hours. While matzo is softening, make syrup.
In small saucepan over moderately high heat, stir together the water and sugar. Bring to boil, then lower heat to moderate and cook, uncovered, until syrupy and thick, about 15 to 20 minutes. Stir in lemon juice and honey and simmer 1 minute. Remove from heat and let cool, then chill until ready to use.
To Assemble the Dessert:
Preheat oven to 350°F. In large bowl, stir together walnuts, pistachios, brown sugar, cinnamon, and cardamom. Separate out ⅙ of nut mixture and reserve for topping cooked baklava.
Transfer 1 sheet of the prepared matzo to the counter. Press a rolling pin once over the sheet from one end to other to flatten. Rotate 90 degrees and repeat. Using a pastry brush, grease the bottom and sides of an 8-inch square pan with the melted butter/margarine. Lay one sheet of flattened matzo on the bottom of the pan, and then spread with more melted butter/margarine. Sprinkle the matzo with ⅕ of unreserved nut mixture. Roll out second sheet of matzo and transfer to pan. Brush with margarine and sprinkle with nut mixture. Repeat with remaining matzo sheets and remaining nut mixture, ending with matzo sheet brushed with margarine on top.
Bake until golden, about 25 minutes. Keeping the baklava in the pan, place the pan on a cooling rack so that it can cool all around, and immediately pour the chilled syrup over. It may seem like a lot of syrup, but the matzo will absorb it all. Sprinkle with reserved nut mixture. Let cool, then cover and let stand at least 8 hours and up to 3 days. (Do not chill.) Cut into small squares or diamonds and serve.