Heat one tablespoon olive oil in a non stick pan. Add the potatoes, salt and black peppercorns.
Mix well, cover and cook till the potatoes are red and crisp. Remove from heat and add one tablespoon lemon juice. To make the marinade, mix soy sauce, fish sauce, salt, black peppercorns, brown sugar, coriander leaves and lemon juice in a bowl.
Add the lamb slices, mix and set aside for an hour. Heat one tablespoon olive oil in a deep non stick pan. Add the lamb slices and stir-fry for two to three minutes.
Add garlic and mix well. Cover and cook on high heat for two minutes and then on low heat till the lamb is cooked. Heat the remaining olive oil in another non-stick pan.
Add the spinach leaves, salt and leek and stir-fry for two to three minutes. Transfer the spinach and leek onto a serving dish.
Place the lamb slices on them arrange the cooked potatoes on all sides. Serve hot.