Add sugar to a saucepan and cook over medium heat until melted and golden brown.
Pour the caramel into a baking dish or individual ramekins and spread evenly.
Blend ripe mangoes with a little milk until smooth.
Whisk eggs, remaining milk, condensed milk, mango puree, vanilla extract, and salt until well combined.
Strain the custard mixture for a smooth and silky texture.
Pour the mango custard over the caramel and bake in a water bath until set but slightly jiggly in the center.
Cool completely, refrigerate for several hours, then invert onto a serving plate and garnish with fresh mango pieces.