Prepare mango puree: In a blending jar, add mango cubes and blend well until pureed. Reserve 3/4 cup of the puree for later use.
Make mango custard: In a wok, combine mango puree (except reserved portion), milk, sugar, and custard powder. Mix well and cook on medium flame, stirring continuously until thickened. Let it cool completely.
Prepare whipped cream mixture: Place a bowl over ice cubes, add chilled cream and beat on low speed for 30 seconds, then on high speed until soft peaks form. Add condensed milk and mango essence, then beat until well combined. Set aside.
Cook reserved mango puree: In a saucepan, mix reserved mango puree, sugar, and cornflour until well combined. Cook on medium flame for 1-2 minutes, stirring continuously until thickened. Let it cool and transfer to a piping bag.
Assemble the bread pudding: Trim bread slices and cut into rectangular shapes. In a serving dish, layer bread slices and mango custard alternately, spreading evenly.
Add cream and garnish: Spread the prepared cream mixture over the top layer. Garnish with the prepared mango puree, sliced almonds, pistachios, and mango cubes.
Chill: Refrigerate the assembled pudding for 2 hours or until chilled before serving.