candy, pastry
餦 centers on sweet, soft food items: candy and pastry. Both meanings share the idea of a confection or treat made from grain or sugar.
餦 combines 飠 (food, eating) with 長, which likely contributes the sound. The character is rare and its exact historical development is uncertain.
The food radical 飠 on the left suggests something edible, and the right side 長 (long) can be imagined as a long, stretched piece of taffy or a long pastry. Together they make candy or pastry.
For チョウ, imagine a long pastry named after a chef called Chou: Chou's pastry -> チョウ. The long shape ties back to the 長 component.