Preheat the grill to its highest setting.
For the griddled mango, score the mango flesh with a sharp knife to make diamond patterns on the surface.
Heat an ovenproof griddle pan until hot, rub the flesh of the mango with the vegetable oil and griddle flesh-side down for two minutes.
Turn the mango over, sprinkle with brown sugar and chilli and griddle for a further 2-3 minutes. Add the rum to the griddle pan and flambé for one minute.
Place the pan under the grill for 2-3 minutes, until the mango is golden-brown and caramelised.
For the praline, gently warm the sugar in a frying pan until the sugar crystals have melted and caramelised.
Add the brazil nuts, stir well to coat the nuts and cook for 1-2 minutes. Add the rum and mix well.
Pour the mixture onto a non-stick baking sheet greased with a little vegetable oil. Leave to cool for five minutes, then break into pieces.
To serve, place the mango onto a plate and sprinkle with the brazil nut praline.
