With a small tub's worth of last week's frosting surviving the week's biscuit needs, salted caramel buttercream was always going to be the frosting of choice for this week's adventure. And having come across the idea of cold-brew coffee a few months ago, I've been meaning to try a batch for a long time. Cold-brew coffee is brewed over 12-24 hours at room temperature before use, and because no hot water comes into contact with the coffee grounds, the acids aren't leached into the liquid, resulting in a much smoother taste, and fewer gastric side effects. For those interested in the caffeine content, cold-brew coffee also contains less caffeine than hot-brewed coffee gram for gram. The main reason for cold-brewing coffee over hot-brewing and then cooling is that coffee that's
gone cold tastes rank, owing to the bitter acidic compounds that are extracted with hot water. So for a decent iced coffee, this is the way. I'm not sure it matters as much if you're using it in a cake, especially as the subtler flavours in coffee that you get to taste with the cold-brew method, were you to drink it instead of bake it, are masked by the other cake ingredients. I've certainly used hot-coffee-gone-cold in cakes before and not had any problems with it, but hey, I was making some anyway.
The first attempt at this cake ended up with a very subtle coffee flavour, especially delicious straight from the fridge with slightly hardened frosting. Personally I wanted something more unmistakably coffee-ee, which the second batch was, though it mellowed over the next day. The recipe is for the full strength cake, but if you prefer a weaker version, decrease the amount of coffee used throughout the recipe by half.
This cake has a couple more stages in it's making than other cakes - the cake is drizzled in a coffee/sugar syrup mixture which needs to be made beforehand and cooled, and the salted caramel frosting requires the caramel to be made and cooled beforehand too. It's worth it though.
Best a day after baking and frosting, and I imagine it would only get better over the next few days, but I can't personally vouch for that.
Lydia's Cold-Brew Coffee Cake
Ingredients
Cake Batter
120g (5oz) butter
300g (1 1/3 cups) caster sugar
2 eggs
120ml (1/2 cup) coffee (see below)
240ml (1 cup) plain yogurt
300g (2 cups) plain flour
1 tsp salt
1 tsp bicarbonate of soda (baking soda)
1 tbsp white wine vinegar
Coffee
Cold-brew method: 300ml (1 1/4 cups) coffee grounds, 300ml water
or hot-brew-gone cold method: 240ml (1 cup) coffee grounds, 300ml off-the-boil water
or 240ml (1 cup) coffee made with espresso powder/wholebean instant coffee powder, I'd make double strength from what the manufacturer recommends as a starting point.
Sugar Syrup
60ml (1/4 cup, 4 tbsp) caster sugar
60ml water
Salted Caramel Frosting
125g (scant 2/3 cup) caster sugar
60ml (1/4 cup, 4 tbsp) water
80ml double cream or cream substitute like Elmlea
1/2 tsp salt (or to taste)
1 tsp vanilla extract
250g (10oz, 2 1/2 sticks, 1 1/4 cup) unsalted butter - softened (if you haven't the time to let it soften at room temperature, you can cut it up into small cubes and whisk it with a hand held mixer, or beat it in a standing mixer until softened)
300g (1 1/2 cups) icing/confectioner's sugar
Method
To make the cold-brew coffee, mix the grounds and the water, let stand for 10 minutes and mix again. Cover and leave at room temperature for 12-24 hours (I had time for a 15 hour wait) then strain and pass through a muslin cloth/cheese cloth to strain out the silty muck.
If making hot-brew-gone-cold method, brew as normal and leave to cool.
For the sugar syrup, bring the sugar and water to the boil in a pan while stirring to dissolve. Leave to cool.
To make the drizzle for the cakes, combine 1/4 cup (60ml, 4 tbsp) of sugar syrup with 1/4 cup of the coffee (if making the weaker version of the cake, make the drizzle up as described here, but use only half of it).
Preheat the oven to 170ºC, (325ºF, gas mark 3, electric oven, 180ºC - 350ºF gas 4 for gas oven).
Line two 8 inch tins with paper (a butter/oil and flour coating doesn't work quite so well for this cake).
Whisk the butter and sugar until smooth.
Beat in the eggs.
Add coffee and beat until smooth. It will be very runny at this stage.
Add half the flour and mix well before adding half the yogurt.
Repeat with the remaining flour and yogurt.
Add the salt, bicarbonate of soda and vinegar, and beat well.
Divide whatever batter avoids death by immediate eating between the two prepared baking tins and bake for 45-55 minutes (now's a good time to make the frosting), until the centres spring back and a skewer comes out clean. It'll have a fizzing sound when baked if you listen closely.
I
mmediately skewer it all over and pour the syrup/coffee mixture over the cakes (1/4 cup, 4 tbsp, for each layer. If you're making the weaker version of the cake, use only 2 tbsp per layer).
Allow to cool in the pan for 10-15 minutes before turning out on a wire rack, upside down, to finish cooling.
For the salted caramel frosting, dissolve the caster sugar in the water over a low heat, before turning the heat up and cooking for 2-3 minutes. The caramel will be bubbling, slightly golden in colour, and thickened. Slowly pour in the cream while stirring - be careful as it will splatter. Once mixed, remove from heat and stir in the vanilla extract and salt and allow to cool. Whisk the butter with the icing sugar until light and fluffy, then add the cooled caramel and blend until just combined.
To assemble, sandwich the two cake layers together with frosting, and cover with a thin layer. Refrigerate for about an hour before adding a second, thicker layer of frosting. This 2-stage process gives a "crumb coating" and will help prevent stray cake crumbs from appearing on the outside of the cake. It's not strictly necessary, but it does look neater, especially with such a crumbly sponge.
Enjoy chilled, with yet more coffee, either brewed the normal way, or using what remains of the cold-brewed coffee, diluted around 1:4 with cold water/ice/milk and a dash of sugar syrup to taste.
