Wasn't able to find suitable synonyms for heart in english so just directly romanized them. If someone can think of something better please change it
I don't think synonyms are necessary. They are both hearts after all. For an English-speaking Kutaka to react that way, it would make the most sense for her to hear the word "heart."
The only potential issue I see is conflict between singular and plural nouns. It makes sense in the original Japanese; the customer asks for one heart (one order of hatsu) and receives one heart (heart hands). In English, it would be more natural to describe hatsu as "chicken hearts" because there would likely more than one on each skewer.
I can't think up of any good solutions to this, sorry.
