An incredibly simple and a-mooo-sing design to create. All that is needed is white polish, a dotting tool and some black polish.
Start by painting your nails completely white. I always take a long time over this because white is notorious for smudging and looking uneven. Make sure the polish is completely dry before adding more coats.
After that I simply used a dotting tool to create some black cloud like shapes to my nails. I aimed to have 3 to 5 per nail depending on the size of the nail and the shape.
Finish with a top coat for shine and there you go...