If you want to make this with fresh vegetables rather than frozen, then up the water (keeping the amount of stock concentrate the same) and indeed I would double it to 500ml / 2 cups. But if using frozen - which is how I make this 99% of the time, and why it is a great storecupboard standby - I find it easier to use a cappuccino cup, or similar, and measure out 1 ½ cups of each frozen green veg rather than weigh it.
This is what to cook when you find out mid-afternoon that you've somehow acquired 6 people for dinner that evening.
Photo by Lis Parsons.
Recipe posted by Nigella