I do know they are edible, but I never tried them. Not sure if they need to be cooked, or if they are safe raw. I remember reading somewhere about a naturalist making mullberry pie.
When I was a young whippersnapper I mowed a place that had a mullberry in the front yard. When I was done mowing the front yard looked pretty strange with all the lines going straight to that mullberry tree Not only are they edible, but when they are good and ripe, they're sweeter than anything you've ever tasted!!