Combine ingredients in a microwave-safe container, and cook on high heat 1 minute. Stir and cook 1 more minute. Let cool to room temperature, then refrigerate until cold.
Put oven rack in middle position and preheat oven to 350 degrees F. Place almonds in a food processor and process with sugar, cinnamon, allspice and salt until almonds are roughly ground.
Generously brush a 13 by 9 by 2-inch glass baking dish with melted butter. Halve phyllo sheets crosswise and stack sheets. Keep stack covered with 2 overlapping sheets of plastic wrap and then a dampened clean kitchen towel. Lay 2 sheets of phyllo in bottom of baking dish and brush top sheet generously with butter. Add a couple of tablespoons of almond mixture. Continue to layer 2 sheets at a time, staggering sheets in each double layer slightly to cover bottom of dish, brushing every second sheet generously with butter and add 1 cup of the almond mixture, until 10 sheets of phyllo have been used, total. Brush top layer of phyllo with butter. Let baklava stand at room temperature to harden slightly, about 10 to 15 minutes.
Using a sharp knife, cut baklava into 6 equal squares, then cut each piece in half diagonally to make 12 triangles. Be sure to cut all the way through.
Bake baklava until golden, 50 minutes to 1 hour. Transfer dish to a rack to cool, then slowly pour cold syrup around edges of hot baklava, in between all cuts, and over top. Let stand at room temperature at least 8 hours. Cover when baklava is at room temperature. Do not chill.
Baklava keeps in an air-tight container up to 1 week.