Add sugar and a pinch of flour in the lukewarm water. Next add yeast, shake a bit to cover it with water. Cover the bowl and keep aside for 7-10 min. The yeast should look activated (frothy at the surface). If the yeast doesn't get activated, do not use it. Sieve flour and combine with salt and oil. Add activated yeast water.

Combine well with lightly. Now add milk, a little at a time and combine dough lightly. Work the dough lightly till it looks smooth.

Heat up the nonstick flat pan (I used dhosa pan). Gently place the naan upside down. Wait till you see plenty of tiny bubbles on the surface of the naan. Then flip it. (Check the video shred above.)

If you wish to store it for later use, take it off the pan before it gets crunchy on any side. See this video that shows the thickness as well as the amount of cooking to be done on both the sides. Place it on a cloth and cover it with the cloth immediately. The cloth will keep them soft.

When they cool down, pile them up, wrap with a foil paper and freeze it. Remove them from the freezer at least 3 hours before using. Apply butter on each naan. Cook them on hot pan, high flame before serving. Cooking on high flame will help them puff well and fully cook them too. Serve immediately. If they cool down, they'll feel chewy.

Personal comments:

Perhaps rolling them ablong also matters when it comes to puffing them on a pan. Roll them round if you want to puff on the direct flame. Perhaps puffing them on pan keeps them soft even after the second cooking. Need to observe this point.