Leeks and Sesame Seed Bread Swirls

Line two baking sheets with parchment paper or silicon pads. Dissolve yeast into a small bowl with ½ cup warm water, adding 1 tsp of salt and 1 tsp of sugar. Let it stand for about 10 minutes, until the mixture bubbles. Sift the flour into the bowl of a stand mixer . Add the remaining 1 tsp of salt and 1 tsp of sugar. Grate the well chilled butter over the flour and rub it with your fingertips until mixture resembles coarse meal. Beat in egg and egg yolk, and add it into the dry ingredients together with the yeast mixture. Scrape down the sides while mixing. Knead on medium speed until dough is soft and smooth, about 5 minutes. The dough will still seem a bit soft. Form the dough into a ball and transfer to a large, lightly oiled bowl. Cover and let rise until doubled in size, about an hour and half. Meanwhile, chop the leeks finely . Transfer it into a medium bowl and stir in toasted sesame seeds, the black pepper and 3 tbsp oil and set aside. Preheat oven to 180 C . On a well floured surface roll dough into a 35cm x 30 cm rectangle. Spoon leek mixture over it and spread it evenly to the corners of dough. Working from one short edge, roll the dough into a cylinder. Cut cylinder into 2cm thick dough swirls and transfer them to prepared baking sheet. Brush lightly with oil and bake until golden brown, about 30 minutes.