Place the minced beef in a bowl with the spring onions, Ras el-hanout, coriander and sesame seeds. Season to taste. Mix well to combine and then roll into 20 even-sized balls. Sprinkle the cornflour on a tray and roll the balls in it to lightly coat.
Heat the oil in a large frying pan and fry the meatballs in batches for 5-6 minutes until cooked through and well browned. Remove with a slotted spoon and drain well on kitchen paper. Leave them to cool a little while you cook the remainder, wiping out the pan and using fresh oil if necessary.
Place a warm meatball in each lettuce leaf and garnish with a mint leaf. Arrange on plate with bowls of chilli sauce for dipping.