Which of the following ingredients is found in the ham and cheese croissant?

The selection of Swiss cheese as the correct answer highlights its role as a key ingredient in the ham and cheese croissant. This type of croissant traditionally includes both ham and cheese as its main components, with Swiss cheese being a classic choice due to its mild and creamy flavor that complements the saltiness of the ham perfectly. Swiss cheese also has a desirable melting quality, which enhances the overall texture and enjoyment of the croissant when baked.

In contrast, while shredded beef, salami, and mortadella may be included in various other sandwich or pastry recipes, they are not typical ingredients associated with a traditional ham and cheese croissant. Thus, the presence of Swiss cheese is what makes it an essential and defining element of the dish.