Final answer:
The custard spade, also known as a portioning spade, is primarily used for option A) proper portioning.
Step-by-step explanation:
The custard spade, also known as a portioning spade, is primarily used for option A) proper portioning. It is a specialized tool designed to measure and serve uniform portions of custard or other soft desserts. The flat, spade-like shape allows for precise cutting and portioning, ensuring consistency in serving sizes. This helps maintain standardization in commercial kitchens, bakeries, or food service establishments, contributing to a professional presentation and efficient service. While it is not typically used for options B or C (flattening custard for scooping or directly scooping custard), its primary function is indeed to aid in the accurate and consistent portioning of soft and delicate desserts like custard.