Whisk 2 tablespoons mango custard powder with 4 tablespoons of the milk until smooth and lump-free.

Heat the remaining milk with 4 tablespoons sugar in a saucepan over medium heat until steaming.

Whisk the mango custard slurry into the hot milk and cook until thickened, about 3 to 5 minutes.

Transfer the mango custard to a bowl and let it cool until no longer hot.

Fold 1 cup yoghurt into the cooled mango custard until evenly combined.

Cut fresh mango into chunks if needed and roughly chop the pistachios, almonds, and cashews.

Arrange half of the 23 plain biscuits in the base of a trifle dish.

Spread half of the mango custard mixture over the biscuit layer.

Scatter half of the mango chunks and half of the mixed nuts over the custard.

Repeat the biscuit, custard, mango, and nut layers with the remaining ingredients.

Garnish with pomegranate seeds, if using, and refrigerate for at least 30 minutes before serving.