Melt unsalted butter. Mix walnuts. sugar, cinnamon and cardamom. Using a pastry brush, brush the bottom of a 9x13 pyrex baking pan with melted butter.
Place syrup igredients into a small pot, bring to a boil, and then turn down to a low flame. Let simmer for approx. 15-20 minutes. Turn flame off.
While syrup is cooking, assemble Baklava. Open phyllo dough and place 2 sheets at a time into buttered pan. Butter every 2 sheets with melted butter. Keep unused dough under a damp cloth to keep from drying out. After 8 sheets, sprinkle 1/2 of the walnut mixture on the top sheet. Continue for another 4 sheets, buttering every 2 sheets. Sprinkle the second 1/2 of walnut mixture. Cover with 6-8 more sheets, buttering every 2 sheets.
Score baklava at a diagonal to create long rows across the 9" side of the pan. Cut mixture along 13" side of pan, top to bottom. I usually cut into 4 sections, this creates diamond shaped pieces.
Bake at 350 degrees 45-50 minutes, until baklava is golden. Remove and re-score pieces. Using a large spoon, drizzle a little syrup on top of each piece of baklava. Be sure to use all of the syrup. Let cool. Cover with aluminum foil to transport or place on a plate to serve. Pieces will be sticky and sweet.