Can I use hazelnut oil instead of olive oil in the olive oil chocolate cake? Or possibly use part hazelnut oil, part olive oil? Thank you.
Nigella's Chocolate Olive Oil Cake (from Nigellissima and on the Nigella website) uses regular olive oil. This oil is slightly midler than an extra virgin olive oil, though slightly stronger than the "mild" version of olive oil and does not hinder the flavour of the chocolate cake.
However some nut oils, such as hazelnut oil, tend to be quite strong in flavour and so should be used carefully. Whilst it would be possible to use some hazelnut oil in the cake we would suggest substituting 1/4 of the olive oil with hazelnut oil.
It is also worth noting that nut oils tend to turn rancid fairly quickly so once the bottle of hazelnut oil has been opened store it in a cool dark place and check it each time before you use it.