Line a baking sheet with baking parchment. Divide the risen dough into 8 equal pieces and shape each piece into a ball on a lightly floured surface. Spread the balls out well spaced apart on the baking sheet and loosely cover with oiled clingfilm. Leave to rise for about 1 hour until puffy.
Meanwhile, preheat the oven to 200C/400F/gas mark 6. Brush the risen buns with the beaten egg and sprinkle with sesame seeds. Bake for about 20 minutes until deep golden, the internal temperature should reach 94C.
Transfer the buns to a wire rack to cool before serving, store in an airtight container.