We asked Harry all about vegetable cake-making from which vegetable to use, why vegetables work instead of butter and for her top baking tips, including tin size, freezing and fresh versus organic...
Which vegetables work for which cakes?
'It's quite complex, but in nutshell, choose the vegetable for the texture and effect you're after. For example, my chocolate heartache cake with aubergine is more of a heavy torte. Aubergine is quite silky and I wanted that silkiness in the cake. For a light, fluffy cake or a Victoria sponge, you want vegetables which can expand and become aerated like a courgette. Weirdly enough, potatoes especially Maris Piper work really well in sponges.'
How do vegetables replace butter?
'Vegetables contain so much natural moisture. If you want the squidgy factor, it doesn't matter how far in advance you grate and puree the vegetables e.g. with brownies. If you're grating veg into a cake for air, for a sponge cake for example, then it's very important to grate at the last minute. Otherwise the water will have left the vegetable and instead of a feather-like consistency, it's wet. You want the moisture to come out in the cake, not before, as you're not using any butter or fat.'
Are there any veg which just don't work?
'I once dreamt of coffee cake with Jerusalem artichokes! I thought that nutty, woody flavour with coffee would be perfect, but it was very bitter, no height, no air - it was like a slab. Funnily enough, it was also one of the first recipes I tried out for the book so I was quite frightened! And remember, the vegetables aren't all inter-changeable - you can't switch swede for carrot for example. Baking can be quite prescriptive and it's important to follow and respect the recipes. I've done a lot of playing around so everyone else can get on with the fun part of making and eating.'
It sounds like a godsend for getting kids to eat vegetables...
'Absolutely. We'd all benefit from eating more vegetables. You can eat too much fruit, but you can't ever really eat too much veg. If your kids just won't eat their veg, this is a great way of compensating.'
Check out our vegetable cake recipes, including Harry's brownies and red velvet cake