1. Preheat oven to 180°C fan forced. Combine the flour and butter in a food processor. Process until the mixture resembles fine breadcrumbs. Add sugar and ½ cup of the macadamia nuts, process until crumble forms clumps. Spread out on a baking tray and bake for 15 minutes or until golden. Cool.
2. Meanwhile, to make the quick salted caramel, pour the cream into a small saucepan, add the caramels. Stir over medium-high heat for 3-4 minutes until cream comes to the boil. Remove from the heat and stir until caramels have melted and sauce is smooth. Stir in the salt. Set aside to cool.
3. Line the base and sides of a 4cm deep, 20cm x 30cm (base) baking dish with baking paper, allowing a 2cm overhang at both long sides. Scatter the crumble over the base of the pan to cover.
4. Peel 3 of the mangoes. Chop the fruit. Swirl chopped mango, remaining macadamia nuts and ¾ cup salted caramel through the ice cream. Spoon over the crumble base. Smooth the surface. Cover and freeze overnight.
5. Peel and chop the remaining 2 mangoes, spoon over the ice cream. Cut into pieces and serve drizzled with remaining salted caramel.