The best type of potatoes to use in soup recipes are all-purpose potatoes (such as Yukon Gold) or waxy potatoes (such as red bliss, peewees, and fingerlings). Waxy potatoes have a high moisture content and are low in starch. High starch and low moisture potatoes (such as russet potatoes and Idahos) are more suitable for baking, due to their mealy texture and tend to lose their shape when used in soups. If you prefer your soups mealy and thick they may be perfect for you though.