Put the flour, salt, sugar and yeast in a large bowl. Add the butter and milk. Mix with a round bladed knife to make a fairly soft dough, adding a dash more hot milk or water if the dough feels dry. Turn out onto a floured surface and knead for 10 minutes to make a smooth, elastic dough. (Alternatively knead for 5 minutes using a free-standing mixer fitted with a dough hook). Place in a lightly greased bowl, cover with cling film and leave in a warm place for about 1 hour or until the dough has doubled in size.