Take a heavy bottomed pan, boil milk first on a high flame, then reduce it after milk has boiled well.
Keep stirring milk at intervals to prevent burning at the base.
Keep pushing back the creamy layers that form on top and sides back into the boiling milk to make it thicker.
After about 1 hour the milk would have reduced and thickened to 1/3 rd the quantity .
Add sugar at this stage, pinch of cardamom powder.
Garnish with slivers of almonds or pistachios or a mix of both.
Peel the mangoes and chop finely or roughly into smaller chunks.
Pour the thick rabdi as much as you like over the chopped fruit and garnish on top with more nuts.
Serve chilled so keep refrigerated till serving time.
Mangoes may also be pulsed lightly and blended with the rabdi while serving though I prefer to pour rabdi over finely chopped fruit.