Mirepoix is a French term for diced carrots, celery and onions. Cooked together in oil or butter, they are used as a flavoring base for sauces, soups, stews, roasted meats, game and fish. Bacon (or raw ham) is often added when using mirepoix to flavor meat dishes.

The mirepoix was first advocated in the 18th century by the cook to the French Duc de Lévis-Mirepoix, hence the name.

Recipe: French Mixed Vegetable Soup (Cookthink)
Recipe: Beef Osso Buco (Cookthink)
Reference: How to dice celery (Cookthink)