Thaw phyllo dough to refrigerator temperature if it is frozen, by keeping it in the refrigerator for 12 hours. 

Preheat oven to 350 degrees. 

Place the sugar, water, maple syrup, rosewater, vanilla, and salt into a saucepan and bring it up to a boil over a high flame.   Once bubbling, turn off the flame under the pot and allow it to cool to room temperature.

Place the pistachios, cinnamon, and cardamom into a food processor and grid for about 60 seconds to form a coarse meal.   Do not process so long that the nuts start turning into nut butter. Take out ¼ cup of the ground pistachios and reserve them to the side to garnish the baklava with later.

Roll out the phyllo dough and cut it down the middle to make two short rectangles.  

Lightly butter the bottom and sides of a ¼ sheet baking pan or 9X13 baking dish using a brush.

Spread two sheets of phyllo dough out on the bottom of the baking pan, and brush with vegan butter. Repeat adding and buttering phyllo sheets, two at a time until there are 8 sheets on the bottom of the pan. 

Spread out ⅓ of the ground pistachios from the food processor evenly over the phyllo base.  Add 2 sheets of phyllo on top of the ground nuts, butter them and then add another ⅓ of the ground pistachios.  Continue like this until all of the filling is used up.   Add the final sheets of phyllo dough to the top, buttering every two layers until all remaining phyllo sheets are used up.

Butter the top sheet of phyllo well. It should look wet and shiny with melted butter. 

Cut the baklava into 6X4 rows, either into squares or diamond shapes with a very sharp knife. This should result in 24 servings. Make sure the knife cuts all the way through to the bottom with every cut.

Place the baklava into the oven and bake for 30-35 minutes until crisp and golden brown.

Remove the baklava from the oven, and pour the sugar syrup over it. While the syrup absorbs, use a sharp knife to carefully re-cut everywhere you had cut before it was baked.  This step is important so that the syrup penetrates into all of the layers. If any syrup pools up in the corners, spoon it back over the top to evenly saturate the whole tray.

While the baklava is still hot and sticky, sprinkle each piece with a little dash of ground pistachios and a couple of pieces of dried rose petals.

Allow the baklava to cool to room temperature before serving.