Measure the flours into a bowl, add the salt and mix thoroughly together. Then warm the flour slightly in a low oven.
To prepare the yeast measure the hand-hot water into a jug, then pour half of it into another jug or bowl. Sprinkle the sugar and then the yeast into one lot of water, stir and leave aside till a good 1 inch (2.5 cm) frothy head has formed.
Now remove the flour from the oven, rub in the butter, then make a well in the centre, stir the yeast liquid and pour it into the well. Pour the other liquid into the yeast jug to rinse it out, then add this to the flour, gradually stirring with a wooden spoon at first and then finishing off with your hands, until you have a smooth dough that leaves the bowl clean.
Now transfer the dough on to a flat working surface and knead it thoroughly for about 6 minutes, by which time it will have become very elastic and springy.
Next divide the dough into 12 portions to form the rolls. If you want your rolls to be absolutely the same size, you can weigh the dough, divide the total weight by 12 and then weigh each individual piece. Stretch each piece into an oblong and fold one end into the middle and the other end over that. Then, with the folds underneath, slap the roll into a round ball. Place the rolls on to the well-greased baking sheets, cover with a sheet of oiled clingfilm, or encase the baking sheet inside an oiled polythene bag. Leave the rolls to rise until they have doubled in size: 35-40 minutes in a warm place or 1-1½ hours at room temperature. Meanwhile pre-heat the oven to gas mark 7, 425°F (220°C).
When the rolls have risen, sprinkle them with flour and bake them on a high shelf of the oven for 20-25 minutes. They should sound hollow when you tap them underneath if they are cooked enough. Cool the rolls on a wire cooling rack.
You will also need one large or two small well-greased baking sheets.