This is another one of those basics that’s used in the Kitchen yet most people don’t really understand. It’s a simple mix of Onions, Carrots and Celery that’s the base to various stocks and sauces in Western cuisine.
The part that most people get wrong is the ratio by weight. It 2 parts Onion, 1 part Carrot, 1 part Celery.
Now keep in mind, there are a few other variations of this. The Cajun/Creole holy trinity replaces the carrots with bell peppers and this is the foundation for dishes such as Jambalaya. The Spanish use onions, garlic and tomato.
The other way I see a lot of people screw this up is that they cook it way too fast. Don’t do this, Mirepoix needs to be cooked slow n low to really let the flavors develop. You want to the mix sweat, not brown. Again, slow n low is the only way to go.
When you’re making stock, you use ten parts (by weight) of Bones to Mirepoix. When you’re cooking at home, you might be tempted to use some kind of bullshit pre-made stock. Don’t do this, you’re better than this.
Now, while this might not be a recipe, I do use it and will refer to it from time to time so it’s a good idea to be familiar with it.