Just as the salad requires a plate and soup requires a bowl, should not the pie tin - required in both the construction and baking of the pie -itself be considered a separate receptacle for serving?
I propose that these three receptacles - and perhaps even additional variations such as the bread bowl, cup, vase, and carafe - are all derived from a singular original food and beverage containing vessel AND THUS a singular original food.
Phylogenetically, this LUCF (Last Universal Common food) is none other than water. Water in cupped hands. Therefor, all foods belong to a single food classification. Different variations and configurations of water.
This debate is done. Let us put it to rest in an unlabeled grave in the same manner as the great 19th century poet John Keats, taken too young and ahead of his time. Across the tombstone for this completed debate lies no name or date, only quothe the line:
“Here lies one whose name was writ in water.”