Arrange the mango slices in 4 ramekins.
Stir together the passion fruit flesh, yogurt, crème fraîche, icing sugar and vanilla extract in a bowl, then spoon the mixture over the mango. Tap each ramekin to level the surface.
Sprinkle over the demerara sugar and cook the brûlées under a preheated hot grill for 1–2 minutes until the sugar has melted. Chill for about 30 minutes, then serve.