As he says, they've acquired the yeast for this from the brewing research centre at Weihenstephan, and hence the puntastic name PHD. It's a very dark brown colour and rather lacking in the head department. No shortage of flavour, mind: there's a thumping great wodge of caramel and milk chocolate at the front, similar to what you get in Czech dark lagers and not a million miles from Munich dunkel. Soon afterwards it turns much more schwarzbierish, drying right out and finishing on a crisp and roasted note.
Overall it's a very clean-tasting beer and is utterly sessionable as a result, though the big sweetness also rewards considered sipping too. A beer for all seasons: get it while it lasts.