Line a colander with a cheese cloth and set over a large bowl .Rinse a large pot with water. Without wiping, add milk. Set on the stove and bring to a boil.
Switch off the stove and add the vinegar. Depending on quality of milk you may need less or more from what's noted in the ingredients. Gently stir 2-3 times. You will see that the milk will curdle and a clear liquid or whey will separate. Add 8-10 ice cubes to help the curds from getting cooked further.
Strain the curds in the colander. Bring the ends of the cheesecloth and make a small parcel. Squeeze a little for 5-10 seconds to drain off. If you used lemon juice for curdling, wash the curds a few times under running water and then squeeze.
Hang the parcel at for height over the sink or with a bowl set below (to catch the liquid) for 30 minutes.
While the chena is draining, add peeled mango along with 3 tablespoon of sugar to a blender jar. If your mangoes are too sweet, 2 tablespoon sugar should be okay. Blend to a smooth puree.
Place the chena in a wide plate and knead it gently using your fingers for 4 minutes. Dont squeeze or use knuckles.
Then, add 3 tablespoon sugar and use the heel of your palm to knead it for another 4-5 minutes. At the end of kneading, you should have a smooth, grain free chenna dough.
To a wide pan (10 or 12 inch) add the mango pulp. To be on the safer side, I always prefer to use non stick pan. Cook the mango pulp on low heat stirring continuously for about 6-8 minutes until its thick and jammy. Dont dry out completely.
Add the kneaded chena, combine well with the mango. Continue to cook for another 8-12 minutes stirring continuously using a spatula. The mixture will start leaving the pan and begin to look like a soft dough. Dont dry out too much.
Turn off the stove and transfer the chena mixture to a lightly greased plate.
Allow it to cool slightly. Do not cool completely else you will not be able to shape it.
Once the mixture is okay to touch, gently knead again for 2-3 minutes. Divide into equal portions. Shape and decorate each portion as you wish.