  We prove a Givental type decomposition for partition functions that arise out
of topological recursion applied to spectral curves. Copies of the
Konstevich-Witten KdV tau function arise out of regular spectral curves and
copies of the Brezin-Gross-Witten KdV tau function arise out of irregular
spectral curves. We present the example of this decomposition for the matrix
model with two hard edges and spectral curve $(x^2-4)y^2=1$
