Threshold cryptosystem with a required share
Here's an easy way to do it:


Take your secret $S$, and select a random value $R$ of the same size, and compute $T = S \oplus R$
Give the accountant the value $R$
Use a $(k-1, n-1)$ secret sharing method to share $T$ to the other parties.


The accountant plus any set of $k-1$ other parties can reconstruct the secret.  And, any smaller subset cannot get any information on the secret $S$.