  For every simple Hermitian Lie group $G$, we consider a certain maximal
parabolic subgroup whose unipotent radical $N$ is either abelian (if $G$ is of
tube type) or two-step nilpotent (if $G$ is of non-tube type). By the
generalized Whittaker Plancherel formula we mean the Plancherel decomposition
of $L^2(G/N,\omega)$, the space of square-integrable sections of the
homogeneous vector bundle over $G/N$ associated with an irreducible unitary
representation $\omega$ of $N$. Assuming that the central character of $\omega$
is contained in a certain cone, we construct embeddings of all holomorphic
discrete series representations of $G$ into $L^2(G/N,\omega)$ and show that the
multiplicities are equal to the dimensions of the lowest $K$-types.
  The construction is in terms of a kernel function which can be explicitly
defined using certain projections inside a complexification of $G$. This kernel
function carries all information about the holomorphic discrete series
embedding, the lowest $K$-type as functions on $G/N$, as well as the associated
Whittaker vectors.
