Chapatis can be reheated but they're best cooked fresh. You could also spread your favourite pickle or chutney over them and roll them into tortilla shapes.
Set aside 200g/7 oz of the flour and reserve for shaping the chapatis.
Place the remaining flour and salt in a deep bowl. Fill another bowl with the cold water.
Add the water to the bowl of flour, a little at a time, kneading as you go, until you have a soft, elastic dough. The longer you knead the dough the softer the chapattis will be.
Sprinkle a little of the reserved flour onto a flat surface or board. Divide the dough into eight and shape each piece into a ball. Flatten the balls slightly, then place one onto the floured board. Roll it out into a flat disc approximately 15cm (6 inches) in diameter, flouring the board when necessary.
Heat a griddle or a shallow frying pan. Lay the chapatti on the griddle or pan and cook for about 20-30 seconds or until the surface is bubbling.
Turn it over with tongs and cook the other side for 10-15 seconds. As soon as brown spots appear on the underside, the chapatti is done.
Repeat with the other seven balls, using the remaining flour to roll them out. Stack them up as they are cooked, placing a sheet of kitchen towel between each one to absorb any moisture.
Spread butter over one side, if you like.