Hi, I was wondering how I would make a black sponge cake? I have black gel colouring, but I was wondering if I have to mix this with chocolate powder first as I would rather make a black coloured vanilla sponge. Thanks!
Unfortunately when food colouring is added to a cake batter it may look quite dark before it is cooked, but during baking the colour tends to fade slghtly so you will end up with a grey coloured cake rather than true black. Also if you add much food colour, even the gel type, you will find that the cake starts to taste more of the food colour (which can sometimes be slightly bitter) rather than of vanilla.
To make a darker cake you would really need to start with a chocolate cake batter and add black food colour to this. We would suggest either using Nigella's Red Velvet cupcake recipe or the Devil's Food Cake recipe from Kitchen (pages 247 and 253 respectively). Add 1 tablespoon of the food colour to either recipe.
Black icing can also be difficult to make and if you are aiming for a very black icing then it would be best to use either a premade black ready to roll (rolled fondant) icing which can be bought from cake decorating stores. You can also buy this type of icing in chocolate flavour and this may darken more easily if you want to knead some black food colour into it. Otherwise a chocolate buttercream will again give the darkest result.