While I am not sure that I understand your question, it seems that you have an analytic expression for the Hessian you want to plot. The syntax of a cutom output function is
function stop = outfun(x,optimValues,state)
So you have the current point x available to your output function, meaning you can calculate the Hessian in your output function.
If I misunderstand what you are asking, please try again.
MATLAB mathematical toolbox documentation