Define a command for italic, bold and centered title inside a quote

Question

Inside my quote, I have a bold, italic and centered header. How can I define a command so that I can typeset this text all in one go? I tried:

\newcommand{\QuoteTitle}[1]{\centerline{\textit{\textbf{#1}}}}

but it just jammed the whole thing on one line!

Here is what I need it to look like, given this input:

\begin{quote}
``\QuoteTitle{Quot paria coniculorum in uno anno ex uno pario germinentur.}

Qvidam posuit unum par cuniculorum in quodam loco, qui erat undique
pariete circundatus, ut sciret, quot ex eo paria germinarentur in uno
....''
\end{quote}

should produce the following output:

Answer 1

I think it might be easier to instead redefine the quote environment to take an optional argument, so that it could be used as

\begin{quote}
...
\end{quote}

or

\begin{quote}[Title goes here]
...
\end{quote}

So, in the code below, that's exactly what I've done, using

\let\oldquote\quote
\let\oldendquote\endquote

and then, borrowing the 'empty' test from What is the difference between \empty and \@empty? to redefine the quote environment as

\renewenvironment{quote}[1][]{\oldquote%
        \if\relax\detokenize{#1}\relax
        ``
        \else
            \begin{center}%
            ``{\bfseries\itshape #1}%
            \end{center}\nobreak
        \fi}{''\oldendquote}

Here's the complete MWE

\documentclass{article}

\let\oldquote\quote
\let\oldendquote\endquote

\renewenvironment{quote}[1][]{\oldquote%
        \if\relax\detokenize{#1}\relax
        ``
        \else
            \begin{center}%
            ``{\bfseries\itshape #1}%
            \end{center}\nobreak
        \fi}{''\oldendquote}

\begin{document}

\begin{quote}
  Qvidam posuit unum par cuniculorum in quodam loco, qui erat undique
  pariete circundatus, ut sciret, quot ex eo paria germinarentur in un
  Qvidam posuit unum par cuniculorum in quodam loco, qui erat undique
  pariete circundatus, ut sciret, quot ex eo paria germinarentur in un
\end{quote}

\begin{quote}[Here's one with a title]
  Qvidam posuit unum par cuniculorum in quodam loco, qui erat undique
  pariete circundatus, ut sciret, quot ex eo paria germinarentur in un
  Qvidam posuit unum par cuniculorum in quodam loco, qui erat undique
  pariete circundatus, ut sciret, quot ex eo paria germinarentur in un
\end{quote}
\end{document}