Nigella's Star Topped Mince Pie pastry uses butter and 'shortening' (as do some American recipes!). Would Trex be ok? And why use both fats and not just butter? Thank you!
The shortcrust pastry for Nigella's Star Topped Mince Pies (from NIGELLA CHRISTMAS) uses a combination of butter and vegetable shortening. Vegetable shortening is a white solid vegetable-based fat and in the UK is sold as Trex, Cookeen and White Flora. In the US the best known brands are Crisco and Earth Balance and in Australia the best known brand is Copha.
For pastry, the combination of butter and shortening gives the best balance of flavour and flakiness. Shortening will give a tender, flaky crust but has little flavour. Butter has good flavour but contains some water, which, when combined with the water added to bind the dough, can yield a slightly tougher pastry. So usually a combination of the two is used, though if you can't find shortening then you can use all butter instead.