Italian has three ways to express the presence of an ingredient in the name of a dish:
the ingredient is the
main or only component of the dish.
e.g. “succo di limone” (lemon juice).
In this case the article is never used before the ingredient.
the ingredient is a
visible component of the dish or used as garnish
e.g. “fragole con panna” (strawberries with cream).
In this case a definite article can be used before the ingredient.
the dish has been
flavored with the ingredient, or tastes like the ingredient
e.g. “gelato al cioccolato” (chocolate ice cream).
In this case the definite article is mandatory before the ingredient, forming an articulated preposition with a.