Mirepoix (French) and Soffritto (Italian) generally contain 2 parts onion 1 part carrot and 1 part celery with some additions and variations. The difference is that the French mirepoix vegetables are cooked slowly in butter, rather than in olive oil for soffritto, and then often removed from the final dish before the end of the cooking process. Mirepoix is cooked low and slow while Soffritto browns the vegetables and cooks them a bit more.