I can't buy Trex or a similar vegetable shortening at the moment due to self isolating at this COVID-19 time. Could vegetable oil be a good substitute and, if so, how much? Love your receipes Nigella and have made many of them which have always been fail-safe. Thank you.
Lily's Scones (from HOW TO BE A DOMESTIC GODDESS) are made with a combination of butter and vegetable shortening (such as Trex). The shortening helps to give the scones a slightly lighter, fluffier texture.
Unfortunately vegetable oil is not a good substitute as it can't be rubbed into the flour in the same way. Fat is rubbed into the flour as the fat coats the gluten-forming protein molecules in the flour. This acts as a protective layer and helps to prevent the scones from becoming too tough when liquid is added, as gluten starts to develop when it comes into contact with liquid. You should also handle the dough as little as possible to prevent gluten from forming. We would suggest using extra butter instead of the vegetable shortening - so use a total of 75g of butter (5 tablespoons).