Key elements of the best chocolate cake ever: the most fragrant cinnamon you can lay your hands on [mine is from The Spice House, a gift from a beautiful friend], nutmeg, vanilla extract, good cocoa powder and espresso powder [if you substitute coffee, go for the strongest you can find and I'd up the quantities even so].
You can find the recipe on Signe Johansen's blog, though I made it from her beautiful book, Scandilicious (see also amazeballs cinnamon buns of yore). My lazy / random idiosyncratic tweaks:
No marbling. Because marbling, srsly? Aint nobody got time etc. And just think of the extra washing up.
Instead, I threw 5 tablespoons of cocoa powder into the whole mix and took out a little of the flour. This creates a seriously tempting (bowl-cleaning-not-a-chore) caramel-tinged batter, with darker flecks of cinnamon and espresso visible throughout:
Baked. Yes, I did tap my tin before shoving it in the oven, but a few air bubbles on the shiny shiny surface are somewhat inevitable because this cake is a miraculous balancing act: simultaneously light and moist.
SJ hid her bubbles in icing; as a home baker who actively prefers her cakes on the fug side, I converted the icing (buttercream infused with the same key flavours of chocolate, coffee and spice) into a filling instead -- far less messy and as a bonus enabling cunning disguise of the fact that you're eating twice the amount of cake per slice....