Step 1 Lightly grease a large ovenproof dish. Place potato in a large saucepan of cold lightly salted water. Bring to the boil, then reduce to medium heat and cook for 10 minutes or until potato is slightly tender. Drain and set aside.
Step 2 Spray a small saucepan with oil and place over medium-high heat. Add onion and cook for 3 minutes or until softened. Add paste and cook for 2-3 minutes.
Step 3 Arrange a third of potato slices in the base of the prepared dish. Layer over a third each of the onion, lime leaves and coriander. Repeat the layers, twice more, with remaining potato, onion, lime leaves and coriander.
Step 4 Place milk and stock in a small saucepan over medium heat and cook until heated. Pour over potato and stand for 30 minutes.
Step 5 Meanwhile, preheat oven to 190°C. Bake for 40-45 minutes, or until potato is golden. Top with extra coriander and serve.