Peel and chop all the ingredients as finely as possible.

You should chop them with a knife, cause the food processor heats them, and this might affect their flavor. But, honestly, I always use the food processor, unless I'm doing a tiny quantity.

When you are ready to cook, heat a couple of tablespoons of extra-virgin olive oil in a pan or pot, and sautè the soffritto for about 5 minutes, medium heat, being careful not to burn the onion.