Cinnamon Cake

Sugar and butter first, beaten together — this is creaming, and what you're doing is beating air into the fat, using sugar crystals as tiny blades to cut pockets into the butter. Those pockets are where your rise starts, before the bicarb even gets involved. "Light and fluffy" is the only instruction that matters here — colour goes pale, volume visibly increases. There's no clock for this; a hand mixer and a stand mixer get there at different speeds, so watch the bowl, not the minute hand.

The cinnamon — six teaspoons is a lot, and that's correct for a cake built to taste of cinnamon rather than hint at it, same logic as why it's called Cinnamon Cake and not Vanilla Cake With A Suggestion Of Spice. If your cinnamon's been in the cupboard two years, it's lost most of its oil and you'll taste dust, not spice; buy it in smaller amounts more often, or compensate by using more than the recipe asks.

Buttermilk: what you actually need is an acidic dairy liquid with enough body to loosen the batter. No buttermilk in the fridge — common enough, it's not a UK staple shelf item — then stir a tablespoon of lemon juice or white vinegar into ordinary milk per 250 ml and let it sit five minutes until it thickens slightly. Plain milk alone won't do; it has no acid to wake up the bicarbonate of soda, and your cake will rise less and taste faintly of soda without the buttermilk's tang to balance it.

Eggs: one egg here is structural, not for richness — it's binding fat and liquid into something that won't curdle apart in the tin. There's a real risk of the mixture looking "split" or grainy right after the egg goes in; that's just the egg not yet fully incorporated into the fat, not a failure, and it smooths out once the flour starts going in.

Baking powder and bicarbonate of soda together, rather than one or the other — the bicarb needs buttermilk's acid and gives a fast, strong lift early; baking powder is slower and more self-sufficient, carrying the rise through to the oven. Leave out the baking powder and rely on bicarb alone and you risk the cake rising fast then collapsing once the acid's spent before the structure's set.

Cocoa in the cake itself is only 5 g — a trace, there to deepen the cinnamon-brown colour and round off the flavour, not to make this a chocolate cake. The icing's 20 g of cocoa is doing the real cocoa work, cut against 400 g icing sugar and balanced by bitter coffee so the topping doesn't sit on the tongue as pure sweetness.

Any neutral butter substitute for baking — anything solid at room temperature with no strong flavour of its own — works in the cake itself; a baking margarine is fine. For the icing, though, use real butter if you can: margarine's water content can make the icing split or go greasy rather than holding smooth and glossy.

The skewer test in step five is there because ovens lie — the fan oven's stated 175°C and the thermostat on your own oven rarely agree exactly, and a shallow wide tin bakes faster at the edges than the centre. A clean skewer tells you what the thermometer and the clock can't: whether the middle, the slowest part to set, has actually finished cooking. Cutting into a cake that looks done but isn't is the single most common way to ruin a sheet bake — the crumb collapses, steam escapes, and you're left with a gummy stripe through the centre.

Letting the cake cool completely in the tin before icing isn't patience for its own sake dressed up as virtue — it genuinely is the ingredient here. Icing onto warm cake melts the butter in it, and you get a thin, sliding glaze instead of a spreadable layer that sets with a bit of structure. Tea with milk alongside, cut into squares rather than wedges — that's the tray-bake habit this cake belongs to, built for a crowd and a big pot of tea, not a formal slice on a plate.