Add the oats, yogurt, mango, banana, milk, and salt to a blender. Blend until smooth and thick like a pourable batter.
Divide the remaining diced mango (for serving) between four jars or containers.
Pour the blended oat mixture over the mango and gently smooth the tops.
If using, stir the melted white chocolate with coconut oil until smooth, then pour over the oats to form a shell.
Seal the jars and chill in the fridge for at least 1½ hours, or overnight, until cold and set.
