Place the lentils in a saucepan with 2 ½ cups water. Bring to a boil over high heat, then reduce the heat and simmer for 30 minutes, or until tender.
Remove from the heat and top up with enough water to just cover the lentils.
Pour in the Burghul, cover and leave to stand for 1 ½ hours, or until the Burghul has expanded.
Drain any remaining water.
For the yoghurt sauce, halve the cucumber lengthways, remove the seeds with a teaspoon and discard.
Grate the flesh and mix in a bowl with the yoghurt and garlic.
Heat 4 tablespoons of oil in a large frying pan over medium heat, add the onion and garlic and cook for 5 minutes, or until soft. Stir in the cumin and coriander.
Add the onion mixture, mint, eggs, flour and salt to the lentil mixture and mix well.
The mixture should hold together enough to drop spoonfuls into the frying pan. If the mixture is too wet, add flour to bind.
Heat the remaining oil over medium heat in a large frying pan.
Drop heaped tablespoons of mixture into the pan (the fritters should be about 2 inches in diameter) and cook for 3 minutes each side, or until browned.
Drain on paper towels, season with salt and serve with the yoghurt sauce.