Mix the flour, seeds, salt, sugar and yeast in the food processor bowl. Add the milky water and butter. Using the dough hook on the food processor, knead for approx. 5 mins. to form a soft, smooth dough. Cover and leave to rise for approx. 1½ hrs. at room temperature until doubled in size. Divide the dough into 4 portions, flatten slightly, shape into balls. Place the balls on a baking tray lined with baking paper, cover and leave to rise for approx. 30 mins.
Baking soda solution
Combine the water and sodium bicarbonate. Flatten the dough balls, brush with the baking soda solution, sprinkle with the seed mix.
Approx. 20 mins. in the centre of an oven preheated to 200°C. Remove from the oven, leave the buns to cool on a rack.
Fill a clean, warm preserving jar with the carrots and onion. Bring the vinegar and water to the boil with the sugar and salt, pour the boiling hot liquid into the jar until it covers the carrots and onion, immediately seal the jar and leave to cool on a towel. Leave to infuse for at least 2 hrs. or overnight.
Combine the yoghurt, mayonnaise and Sriracha sauce, season with salt. Heat the oil in a non-stick frying pan. Fry the burgers for approx. 3 mins. on each side. Remove, keep warm. Cut the buns in half crosswise, spread the Sriracha sauce on the cut surfaces. Place the burger, cucumber, pickles and cress on the bottom half of the bun, cover with the top half of the bun.