What is a characterising ingredient?

* Defines its flavor profile: It contributes a distinct and recognizable taste, aroma, or texture that is essential to the overall impression of the dish.

* Sets it apart from similar dishes: It makes the dish unique and distinguishable from others in its category.

* Cannot be easily substituted: Replacing this ingredient would significantly alter the dish's character.

Examples:

* Tomato sauce in pasta sauce: Tomato sauce provides the tangy, savory base that defines a classic Italian pasta sauce.

* Chocolate in brownies: The rich, decadent flavor of chocolate is the defining element of brownies.

* Ginger in gingerbread cookies: Ginger provides the distinctive, spicy flavor that sets gingerbread apart from other cookies.

* Cinnamon in apple pie: Cinnamon gives apple pie its warm, comforting, and slightly sweet flavor.

In essence, a characterising ingredient is the "star" of a dish, the element that makes it what it is. It's not just a flavoring agent, but a defining component of the dish's identity.