Peel the mangoes using a vegetable peeler. Slice the cheeks off one and cut into small dice. Set aside.
Cut the flesh from the remaining mango and stone, then purée flesh in a liquidiser. Squeeze out the seeds from 2 of the passion fruit halves and mix with the mango purée. Add lime juice to taste. Gently fold the yogurt and half the diced mango through the fruity purée.
Divide between 4 glasses and top with the remaining diced mango. Cover and chill for 30 mins before eating. Scoop the seeds from the remaining passion fruit over the top of the fools to serve.