I want to make a subtitle for a chapter, having \Large as the chapter's title font size; so I'd write it as
\documentclass{book}
\begin{document}
\tableofcontents
\chapter{Title \\ {\large Subtitle}}
\end{document}
This would make the subtitle's font size look good where the title is, but look horrific in the toc. So I'm asking, is there any kind of command or workaround so that will decrease subtitle's font size by one size, in both occasions? From \Large to \large in the chapter and from \normalsize to \small in the toc.
Thanks in advance