If i substitute dark muscovado sugar for castor sugar in baking, will i end up with a big mess?

[TwoPoundCharityShopShoes]

I am baking for a charity cake sale and have run out of sugar, i have a box of dark muscovado will it be... different?

TIA

Depends if you're baking a light Victoria sponge or a fruit cake? Fruit cake, go for it, Victoria sponge - not so much

Thats what i thought all! Bugger, off to the Spar! Thankyou :)

It will be different but I've been known to bung it in anyway!