"It was by this time about nine in the morning, and the first fog of the season. A great chocolate-coloured pall lowered over heaven, but the wind was continually charging and routing these embattled vapours; so that as the cab crawled from street to street, Mr. Utterson beheld a marvellous number of degrees and hues of twilight; for here it would be dark like the back-end of evening; and there would be a glow of a rich, lurid brown, like the light of some strange conflagration; and here, for a moment, the fog would be quite broken up, and a haggard shaft of daylight would glance in between the swirling wreaths."
Jenni Calder notes in her introduction to my edition of Stevenson's Strange Case of Dr. Jekyll and Mr. Hyde (from which that passage comes, and which we're talking about here) that the atmosphere of the book is one of its most memorable features. "The setting is London," she goes on, "but the ambience is without doubt Edinburgh, the Edinburgh of the Old Town's dark wynds and closes, where the turn of a corner could, in Stevenson's day and even now, abruptly leave behind the world of surface respectability, and the lingering shades of Burke and Hare, the grave-robbers, and Deacon Brodie, cabinet maker by day, criminal by night, still flavoured the atmosphere."
So I've made not a cake to go with the book, but a pudding: the appropriately named Edinburgh Fog, as the recipe says, "thicker than the mists that envelope the city today, but like Edinburgh itself, deliciously rich and elegant."
I hope RLS (local lad that he was) would approve.