Bibliography with biblatex: how to create additional labels using authoryear-style?

To achieve the desired result the simplest way is to redefine the begentry hook to print the labelname and labelyear.

\renewbibmacro{begentry}{%
\textbf{\printnames[][-\value{liststop}]{labelname}~\printfield{labelyear}\printfield{extrayear}}\\}

EDIT inserted \printfield{extrayear} to handle the case of multiple labels with the same combination of author-year.