Suppose I want to write a book, where one of the characters is a simpleton without a proper education. This character needs to say "чё?" ("чо?") instead of "что?", e.g.:
— Твоя сестра умеет готовить минестроне?
— Чё \ Чо за минестроне такое?
How should I spell it: "чё" or "чо"? And what are the rules that regulate the spelling in this case?
EDIT: I do not want to portray any specific accent, I am simply asking, what vowel should I use if I want to follow the rules of the Russian orthography.