Peel the skin of the mangoes and cut them into long quarters. Discard the stone and cut them into further thinner slices. Each slice should be about a cm and half thick (or a cm, its upto you).
Wash the mangoes under running water and then in a saucepan or a kadai, just drop them under medium heat. Sprinkle turmeric powder and stir .
Cover the mangoes for 2 minutes and then reduce the heat. In about 5 minutes, the mangoes becomes soft.
Add 5 cups of water and give it a boil. After that let it simmer on medoium heat while covered until the magoes have become pulp.
Add sugar at this point of time. The quantity of sugar will depend on the tartness of the mangoes. More or less 1/2 a cup does but sometimes a few mangoes are too tart and may require some extra sugar.
Let the sugar dissolve and then give it one more boil for about 2 to 3 minutes.
In a separate skillet, heat refined oil and add dried red chili and the mustard seeds. When the mustard seeds start to splutter and the red chili has browned, add that to the mangoes.
Boil it for another couple of minutes and then turn off the heat. When it cools down, store in the refrigerator and have it chilled at the end of your lunch.