Sprinkle the yeast over the measured warm water, stir well and set aside for 10 minutes until it goes frothy. Sift the flour and salt into a large bowl and add the butter. Rub the butter into the flour until the mixture resembles fine breadcrumbs. Add all the seeds and stir. Make a well in the centre and add the yeast mixture. Stir well with a wooden spoon, then use your hands to mix to a firm dough.
Knead for 5 minutes until the dough feels firm, elastic and no longer sticky. Return to the bowl, cover with clingfilm and set aside in a warm place for 30 minutes until the dough has doubled in size.
Turn out the dough and knead again to knock out the air, then divide into 12 pieces. Knead each piece briefly, then form into a roll shape, or roll each piece into a long sausage shape and form into a loose knot. Place the rolls on a lightly greased baking sheet, cover with a clean tea towel and set aside in a warm place for 30 minutes until almost doubled in size.
Mix the egg yolk in a small bowl with a pinch of salt and the measured water and brush over the rolls to glaze. Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 15–20 minutes until golden and sounding hollow when tapped lightly on the base. Remove from the oven and allow to cool a little. Serve warm with soup.