Place mango, milk, cashews, yogurt into a blender, and blend until very smooth. It may take a while, and you may need to scrap down the sides periodically.
Once completely smooth, taste and add maple syrup (optional) one tablespoon at a time until desired sweetness is reached.
You can serve the lassi as is, or you can choose one of the spices listed as a flavoring option (my favorite is cardamom!)
Keep cold until ready to serve -- enjoy!