First, let us precisely define what we mean by a julienne: it is a matchstick cut, bewteen 6 and 7 centimeters long, with a square cross section about a millimeter and a half on a side. The words "between" and "about" in my definition of a julienne might lead the reader to think that some variability is permissible in a julienne cut, and indeed this definition does allow for some variance. But the key is that any variance occurs only from one dish to the next; within a given dish, the cut should be identical. (Really there should not be variability within the same kitchen, because you'd like to be able to use your julienned carrots in any dish with the expectation that they will always have the same cooking characteristics.) With this in mind, we'll revisit the definition. A julienne is between 6 and 7 centimeters, but when you julienne, say, four carrots to make a dish, the resulting couple of cups of matchsticks should all be the same length, without that 1 centimeter difference. Even more importantly, the cross section should be square. If your cut comes out so that it is 1.3mm x 1.6mm, then that is not square, and Chef Marc or Chef Matthew (if you happen to be doing this in a room on the fourth floor of the FCI) will quietly tell you that you do not have a julienne and perhaps you might try again. Further, the square cross-sections of all of your matchsticks must be the same size: you cannot have some that are perfect 1.3mm squares and others that are perfect 1.6mm squares. This is perhaps most important, because cuts of different sizes will require different cooking times to be perfectly done, and so cannot be used efficiently in the same pan or dish.
I describe julienne in such excruciating detail so that you might be sympathetic with me when I tell you that, for the most part, I cannot cut any large quantity of julienned carrots to save my life. But I hope with time I'll get better at it.
I've noticed, in the course of cutting a lot of carrots, that the carrots I get at one of the very nice groceries I go to in New York, Garden of Eden, really do not compare in either appearance or flavor to the ones that FCI buys. At school, the carrots are a solid and deep orange, both after cutting and after cooking. As I cut my store-bought carrots, I notice that a lot of my little matchsticks are so lacking in color that they are almost translucent even when raw.
This brought to mind something I remember reading in a book by one of the best authors of cooking instruction books around, James Peterson, who included this in his book Glorious French Food:
In French cooking, the carrot is nearly as important as the onion. ...[W]hen I mention to assembled guests that we're having carrots as a vegetable, there are no oohs and ahs as there might be for, say, asparagus. This isn't the carrot's fault -- the blame rests with the innumerable restaurants and cooks who have served up carrots boiled and drained, and, if the diner is lucky, dolloped with a pat of butter.
He goes on to describe one of the first methods of cooking we learned for vegetables on our first day of class, cooking à l’étuvée, which is in a shallow pan with butter, covered with a round of parchment paper gently pressed onto the vegetables with a hole cut in the middle to let steam slowly escape, and just enough water that it will be completely evaporated right when the vegetables are done cooking, leaving them in a glaze of butter sweetened by their natural sugars.
Chef Marc emphasized that vegetables are considered properly cooked when the point of a knife meets no resistance at all as you push it all the way to the middle of a piece of the cooked vegetable. Commenting on the current fashion of serving very crisp vegetables, in his French accent that makes things sound both serious and entertaining at the same time, he said, "Maybe someday, when you become famous for your duck à l'orange, you will serve your vegetables however you like, but while you are here, first you will learn to cook your vegetables properly."
So much you can learn from a carrot. When we have our first exam, if part of it entails cutting a julienne, I hope the target vegetable will be turnips. But I know it will be with carrots.