1. Place all the dough ingredients into the mixer bowl in the order listed. Knead until a soft dough forms. Place it in a greased bowl and let it rise for 1-2 hours until it at least doubles in volume.
2. Put the onion in a pan with 1 tablespoon of olive oil. Sauté gently until golden brown. Put all the filling ingredients into a bowl and add the sautéed onion. Mix to combine.
3. Divide the dough into 4 pieces. Roll each piece into a rectangle approximately 30x40 cm. Sprinkle each piece with 1/4 of the filling and roll it up into a log.
4. Join the two ends of the log with a little egg. Make 6 small slits, about 1 centimeter deep, all around the 'halloumotis' (stuffed bread). Brush with egg and sprinkle with sesame seeds.