Prepare you coffee ahead of time and let sit in fridge or freezer until nice and cold. It can be slightly frozen but not completely. If you are making homemade white chocolate syrup. Follow these simple instructions. In a microwave safe measuring cup or mug, heat milk and half and half just until warm. Not hot. Set a side for just a minute.  Place chopped white chocolate in a microwave safe bowl, pour warmed milk mixture over chopped white chocolate. Gently mix. Place in microwave for about 20 seconds. Take out, stir. Put back into microwave for another 20 seconds. Mix again. Once you have a nice smooth and creamy texture, your syrup is ready to go. Set aside for just a minute or so to cool down slightly. If you are using store bought, skip the last step and proceed with step 3.Add cold coffee, ice cubes, vanilla, and powdered sugar into blender. On low speed, pulse until some of the ice breaks up. Do this a couple of times. Now, pour the white chocolate syrup into the blender. Turn the blender back on low speed or pulse a few times. Then, put on medium to high so everything gets blended to a thick, pourable consistency. Taste before pouring. If you like your frappes extra sweet add more powdered sugar. If you want the frappe really thick, add a few more ice cubes. When done, pour into cup(s) and top with whipped cream and sanding sugar if using.  Enjoy the deliciousness!