Now, I’m sure you can make these thin strips using a knife and sweet chopping skills, but we invested instead in a vegetable julienne peeler (this exact one actually) and have found it to work a treat!*
To cook, we just stick them in a microwave proof bowl and microwave for a couple of minutes on high, stirring every minute of so. You can also steam them, but you are more likely to end up with mushier vegetables ( or at least *I* am!) and microwaving is way quicker anyway.
*Note: You will be left with some pieve of vegetable which you can’t further julienne with the peeler (or it becomes hazardous to your fingers to do so!). I normally just chop them up as finely as I can and add them to the mix – or you can just eat them as a raw snack before dinner!!