What flavour did the first porters have? Empyreumatic, I reckon – a word you can easily work out the meaning of yourself (that “pyre” in the middle is the clue), which basically translates as “the taste or smell of something burnt”.
Henry Stopes, author of Malt and Malting, published in 1885, uses it in his description of the making of “brown, blown, snap or porter malt”, talking about how the porter malthouses of Bishop’s Stortford, on the Hertfordshire-Essex border, and elsewhere burnt faggots of beech-wood or oak under the wet malt to dry it, going slowly at first until almost all the moisture has been driven from the malt, then building up the fire so that the sudden violent heat makes the malt grains pop, growing 25 per cent in volume, and
the nature of the fuel employed communicates, very agreeably, the empyreumatic properties that distinguish this class of malt.”
In other words, it tasted burnt and, probably, smoky as well from the initial drying over wood at a lower heat.