Sift the plain flour into a large bowl or the largest bowl of a food processor. Add the diced butter and either rub in with your fingertips, or, if using a food processor, pulse until the mixture resembles fine breadcrumbs. Add the salt and mix again.

Gradually add the liquid by starting with 1 tbsp milk or water, then adding a little more until the mixture comes together to form a dough.

Tip the mixture onto a surface and gently bring it together with your hands, then shape into a disc.

Wrap in cling film and chill for at least 20 minutes before using.