Mirepoix
Mirepoix is, by definition a mixture of aromatic vegetables that are used to provide a pleasant yet subtle background flavor, in order to support and improve the final dish.
Traditionally, mirepoix is the French name of a combination of onions, carrots and celery. Nowadays, in a professional kitchen, the term mirepoix generally defines various mixtures of aromatic vegetables that are used to strengthen the flavors of dishes, or introduce new ones.
The basic mirepoix formula is made from 2 parts onion, 1 part celery and 1 part carrot, mostly used to flavor stocks, soups, gravy and stews.
Here are some variations for you to use:
White mirepoix: (used in white stocks and sauces)
2 parts white of leeks
1 part celeriac
1 part parsnips
Asian Aromatics: (used in stir fries and sauces)
2 parts ginger
2 parts garlic
1 part scallions