This traditional Mediterranean pastry makes a lovely ending to a holiday meal.
Preheat oven to 350 degrees. Combine nuts, cinnamon, allspice, and cloves in a bowl.
Unroll phyllo; halve crosswise. Immediately cover with plastic wrap and then a damp towel. Keep covered while working.
Brush a 9-by-13-by-2-inch baking pan with melted butter. Lay 1 sheet of phyllo in pan. Lightly brush with butter; cover with another sheet of phyllo, and butter again. Layer phyllo and butter 5 more times, ending with phyllo.
Sprinkle phyllo with 2 tablespoons nut mixture. Lay 1 sheet of phyllo over, brush with butter, and cover with a sheet of phyllo. Sprinkle with 2 tablespoons nut mixture; repeat layering with butter, phyllo, and nuts until filling is used up, for a total of about 21 layers. Lay 1 sheet of phyllo over; brush with butter. Layer phyllo and butter six more times.
Using a sharp knife, score the surface of the pastry (1/4 inch deep) diagonally into diamonds (about 2 inches long). Bake until golden brown, about 40 minutes. Let cool on a wire rack for 5 to 10 minutes.
Meanwhile, place sugar and 1 cup water in a saucepan; bring to a boil over high heat. Reduce heat; simmer 3 to 4 minutes.
Pour the syrup over surface of baklava; let cool completely. To serve, use a sharp knife to cut into pieces along scored lines.