Put the flour in a large bowl. Rub in the butter, or margarine, add the salt and yeast. Pour in about 200ml tepid water and mix to a soft dough, using a palette knife, then your hand.
Turn the dough out on to the work surface (try not to use too much flour) and knead well for 5-10 mins, until the dough is smooth and elastic. Shape into a ball, put back into the clean, lightly oiled bowl, cover with oiled cling film and leave in a warm place for 20-30 mins for the dough to prove.
Turn the dough out and “knock it back” (knead) for a couple of minutes. Shape into 6 buns. Put the buns on a lightly floured baking sheet, cover with oiled cling film and leave for about 15 minutes to puff up while the oven heats up. Set the oven to 220°/425°F/Gas Mark .
Glaze the buns with egg. Sprinkle with sesame seeds. Bake for 15 -20 mins until well-risen and golden. Cool on a wire rack. Split and fill the buns with burgers.