In a bowl, mix the flour with all the other ingredients up to and including the yeast. Add the water and oil, mix and knead to form a soft, smooth dough. Shape the dough into 6 balls, place on a baking tray lined with baking paper, cover and leave to rise for approx. 1 hr.
Brush the buns with the oil, sprinkle with Fleur de Sel.
Bake for approx. 20 mins. in the lower half of an oven preheated to 210°C. Remove from the oven, allow to cool on a cooling rack.
Heat the oil in a large frying pan. Sauté the onion, garlic and carrots for approx. 3 mins. Remove from the oven and allow to cool a little. Mix the meat with the vegetables, season, knead well by hand until the ingredients form a compact mass. Shape the mixture by hand into 6 patties, fry in the same pan in a dash of oil for approx. 4 mins. on each side.
Cut open the buns, spread a little yoghurt over the bottom half of each bun. Put the rocket and tomatoes on top, followed by the burgers, avocado and remaining yoghurt. Cover with the top half of the bun, press down gently.