Mirepoix is the basis for so many stocks and sauces that it really deserves a bit of discussion.
At its most basic it simply represents a collection of finely cut vegetables sautéed in oil or butter. Traditionally the three main components are onions, carrots and celery, but other flavourful vegetables such as bell peppers, asparagus, garlic, mushrooms or zucchini can be added or substituted. Another addition that I like to include is fresh chopped parsley or chives. Your choice of components comes down to an intuitive understanding of what will go best with the finished dish.
I try and keep the proportions of cut vegetables fairly even (maybe a little heavier on the onion) and scale up or down as required. The example shown above involves a single small onion, a medium to large carrot, a stalk of celery and a good hank of flat leaf parsley. Unless used in a dish where the finished vegetables will actually be eaten whole, the chopping doesn’t have to be particularly precise–just small enough to saute easily and quickly. The only vegetable that needs to be cut finely is the carrot–mostly because it takes the longest to cook and soften.
Melt the required amount of butter in a non-stick or regular heavy bottomed saucepan over a medium heat. If the recipe calls for caramelizing or browning the vegetables a regular pan is best, because it can take the heat required and works better for deglazing. Olive oil can be used if you are concerned about saturated fats in your diet, but nothing beats the flavour of butter (in my humble opinion).
Add the vegetables to the butter and saute to soften. The length of time required will vary with the amount of heat applied, the quantity of vegetables and even the size of pan used so I can’t offer a definite guideline, but I would plan on at least 20 minutes or so–longer if you plan on browning the vegetables. On that note I would recommend sauteing the vegetables until almost done before increasing the heat a little to brown. This will prevent the butter from browning before the vegetables have finished cooking and will reduce the amount of water in the mirepoix. You’ll just have to experiment a little and find what works best for you (standard operating procedure in my kitchen).
Next comes the wine. What’s traditional french cooking without the wine? As I note on my condiment page, a simple unoaked sauvignon blanc is my cooking white wine of choice. It has lots of fruit flavour and for the most part low tannin and acid. If you’ve ever had cream curdle with the addition of wine, you’ll understand why a low acid wine is best. I also like the subdued flavour profile of sauvignon blanc because it doesn’t overpower a dish–cooking wine should be a supporting character and not the star of the show.
Add the wine to the now cooked mirepoix for a little softening, a little flavour and to deglaze the brownings if any. Add enough to moisten the vegetables, but not drown them if you will be eating the finished vegetables in a dish, add more if it will form the base for a stock. Saute the vegetables and wine at least until the alcohol in the wine has evaporated, but before it begins to lose flavour. If using for a stock, I like to add a little water or bullion at this point. Alternatively, when you go to strain the vegetables in the next step, hot water can be used to rinse the finished mirepoix and extract more flavour. You can “finish” the mirepoix at this point with the addition of fresh chopped herbs, salt, pepper, etc. if desired.
Straining the mirepoix into a heatproof container is the final step in producing your base stock. I’m fortunate enough to have a traditional metal cone-shaped sauce strainer (another thrift store find courtesy of my wife), but if you don’t, fear not–simply line a fine sieve with a cheesecloth slightly larger than the sieve, add the vegetables and when mostly drained gather up the edges to create a ball and (when cool enough) squeeze as much liquid from the ball as possible.
Your mirepoix based stock is now good to go. It can be used as is in any number of dishes or as the base for other more elaborate sauces. For use in some sauces where colour is important, using neutral coloured vegetables such as parsnips and white mushrooms in place of the carrot and parsley is suggested–but I personally don’t bother too much with such considerations.
One last thing. I hinted above that the resulting mirepoix can be eaten rather than used as a stock base. While I won’t provide a recipe here, at some point in late summer or early fall when the Pacific salmon start to run, I will post a recipe for saumon au papillote that uses the soften vegetables as a key ingredient.