"Dear xx, I hope this email finds you well. I am xx who interviewed for the production role over the phone earlier. In case I may not have presented myself nor come off prepared as well as I should've, I just wanted to express that I have a bit of a stutter made worse over the phone and am available in case you want to reach out for further clarification. I was in two minds about sending a following email, but I didn't want to risk losing out on my dream job nor you on a fully qualified candidate for the little that may have got lost in translation. Kind regards, xx."