Sprinkle yeast and sugar over warm milk. Ensure that milk temperature is not above 39˚C – an easy way to check without using a thermometer is that it should be just a little warmer than your skin. Keep aside till mixture bubbles and becomes frothy.Sift together flour and salt, rub 4 tbsps. of the ghee into flour until nice and incorporated. Then make a well in the center.Pour curd and yeast solution in it and keep for 10 minutes.Knead into a soft, smooth, elastic dough, adding more water as necessary to ensure that the dough remains soft and loose. This is a high hydration dough, in order to encourage rising.Put dough in a large bowl and keep aside, covered for 10 hours or overnight.Divide dough into 5 equal balls and place on a greased baking tray.Keep aside for 15 minutes. Roll into thick circles about 10 inches across.Make divots in the dough using your fingers in order to achieve a crosshatch pattern.Keep center slightly thinner than the edges. Preheat oven at 350 C.Brush Roghni Naan with leftover milk, and then generously sprinkle on sesame seeds.Wet bottom and place onto baking tray. Make as many as will fit in the tray.Bake for 4-5 minutes or till done.Remove from the oven and brush the hot Roghni Naan with ghee. Serve hot with curries or vegetables.