Which pastry ingredient is primarily used for decorative purposes and can be sculpted when dried?

Gum paste is specifically designed for creating decorative elements in pastry and cake decorating. It is a sugar-based fondant that dries hard and can be sculpted into intricate shapes, making it ideal for creating flowers, figurines, and other ornamental designs that require fine details. The versatility and ability to hold detailed shapes once dried set gum paste apart from other pastry ingredients.

In contrast, cream is typically used for fillings and toppings rather than for decorative techniques. Pâte à choux is a light pastry dough primarily used to make éclairs and cream puffs, which are meant to be eaten rather than sculpted for decoration. Brioche dough, a rich bread dough, serves as a base for baked goods and has no properties suitable for detailed decorative work. Thus, gum paste stands out as the ingredient dedicated primarily to decorative applications in pastry arts.