[Tex/LaTex] the correspondence symbol with a hat or wedge over equals

Question

I would like to produce a new equal symbol looking like this.
.

What is the best way to do that ? Pure TeX ? TiKz ?

I'm looking for ways to do that rather than to a ready to use solution such as to be able to other new symbols alone.

Answer 1

Before somebody suggests MnSymbol…

\documentclass{article}
\usepackage{amsmath}

\makeatletter
\providecommand{\hateq}{\mathrel{\mathpalette\my@hat@eq\relax}}
\newcommand{\my@hat@eq}[2]{%
  \begingroup
  \sbox\z@{$\m@th#1=$}%
  \ooalign{%
    \hidewidth\raisebox{-0.3\ht\z@}{$\m@th#1\widehat{}$}\hidewidth\cr
    \box\z@\cr
  }%
  \endgroup
}
\makeatother

\begin{document}

$A\cong B\hateq C$                           

\end{document}

With \hat instead of \widehat:

\documentclass{article}
\usepackage{amsmath}

\makeatletter
\providecommand{\hateq}{\mathrel{\mathpalette\my@hat@eq\relax}}
\newcommand{\my@hat@eq}[2]{%
  \begingroup
  \sbox\z@{$\m@th#1=$}%
  \ooalign{%
    \hidewidth\raisebox{-0.2\ht\z@}{$\m@th#1\hat{}$}\hidewidth\cr
    \box\z@\cr
  }%
  \endgroup
}
\makeatother

\begin{document}

$A\cong B\hateq C$

\end{document}