Pound all the dry rub ingredients and 1 teaspoon each of sea salt and black pepper in a pestle and mortar until fine.Split the minced lamb into 6 pieces, and with wet hands, shape into patties about 1.5cm thick. Pat the dry rub all over the burgers, then drizzle over a tiny bit of olive oil.You can either cook the burgers on a barbecue or indoors on a griddle – either light the barbecue and prepare a hot side and a cooler side, or if cooking indoors, heat a large griddle pan over a medium-high heat.Cook the burgers for 6 to 7 minutes on each side, or until done to your liking, then remove to a plate.Quickly halve and lightly toast the buns on the cool side of the barbecue or in the griddle.Spoon the yoghurt into a small bowl and dollop the harissa on top. Squeeze over a little lemon juice to loosen, then ripple the harissa through the yoghurt and drizzle with extra virgin olive oil. Pick the mint leaves.Spread some harissa yoghurt onto the bases of the toasted buns, top with the burgers, squashing them gently into the buns. Add a little more yoghurt, then squeeze the remaining lemon juice over a the mint leaves and place on top. Delicious served with a seasonal salad.