Soak sago in water(till immersing level) for an hour. Rinse it to remove excess starch.
Now boil water and add the sago.
Cook sago till it gets transparent and soft.
Keep mixing else it will stick to the bottom.
Drain water and wash again in running water, drain water completely and set aside.
In a mixer : add mangoes, sugar and 1/4 cup milk and grind it to a smooth paste.
In a mixing bowl add remaining 1/2 cup milk and mango pulp and mix well without lumps.
Now add condensed milk. Mix well with a whisk.
Add cooked sago little by little and mix well.
Now add chopped mangoes (reserve a tablespoon for garnish) and give a quick mix.
Chill it for an hour and serve chilled.
Serve Mango Sago chilled with cut mangoes as topping.