From memory the author was talking about porridge, but we're talking about coffee.

If you want to find out if your coffee roaster really knows how to roast, here's an easy way to cut through the hyperbole; let your black filter or vacuum coffee go stone cold and then try it.  

What better time of year to get something stone cold than right now? (assuming you are in the northern hemisphere)  About 20 minutes will be long enough to get your coffee stone cold.

If your roaster is on their game it will taste unusual at first, but once you get past the shock of the 'cold' part of the equation the coffee should be quite drinkable and you should find yourself acquiring a bit of a taste for it by the time you get to the bottom of the cup.

Any burn tones will be instantly detected.  Drinking your coffee stone cold acts as a magnifying glass for your taste buds, making it much easier to detect any deficiencies in either the green coffee (e.g. mouldy beans) or the roasting process that followed.

While this experiment can also be run on espresso coffee it is a manoeuvre for advanced palates as to the beginner stone cold espresso is going to taste vile, even if its good.

Indeed if you find an espresso roaster in Napoli in a quiet moment (we did) they will admit that one of the reasons there is so much emphasis in southern Italian espresso culture about keeping the cups piping hot is that once their very dark roasts start to cool the sooty notes quickly become overbearing, to the point of becoming unpleasant.  Don't believe us?  Try it in the comfort of your own home some time with a chimney sweep espresso roast of your choice.

In summary, we find drinking our test roasts cold a very helpful tool in deciding whether we are getting close to our target roast profile.