The most most common version of the Holy Trinity (in cooking
Onions, celery and bell peppers.
Although it varies slightly from region to region; most chefs will use garlic just as prevalently. The name should probably reflect four ingredients but would lose its marketability. Some of the more Spanish influenced areas would substitute the celery for tomatoes and call this the Holy Trinity.
Cajun and Creole cooking both make use of the Holy Trinity for the basis of most dishes. There is a matter of opinion on exactly what the Holy Trinity is comprised of and each cook will swear that theirs is right. Even the definition of Cajun and Creole is subjective. Creole was originally the wealthier class and looked down on Cajun cooking. What we know today as Cajun or Creole is actually a subtle marriage of the two (and probably other styles) all a big ball of delicious food that is Louisiana cooking. Never question a Louisiana mom on her choices for the Holy Trinity or you will get yourself slapped – and you would deserve it.
The Holy Trinity is added early to the dish and seasoned very specifically according to the chef. Many will only use salt and red or black peppers for taste. Historically it’s derived from Mirepoix, a vegetable mixture used in French stocks. It’s comprised of one part celery, one part carrot and two parts onion. Combined with Bouquet Garni (another trinity of bay, parsley and peppercorns) it’s the basis for all good French soups.