Place the lamb in a medium pot. Add enough water to cover the lamb
Place the pot over medium-high heat. Bring the water to a simmer. Then reduce the heat to medium-low or low.
Cook the lamb for 20 to 25 minutes, until just tender.
Drain the lamb and set aside for later.
Heat the vegetable oil in a heavy-bottom skillet or Dutch oven over medium heat.
Add the sliced onions and cook the onions, stirring often, until deeply browned.
Add the ginger garlic paste and cook for 1 minute.
Add the turmeric, ground coriander, ground cumin, paprika, red chili powder, and half of the black pepper and stir for 30 seconds.
Add the cooked lamb, salt and stir until the lamb is coated in the onion and spice mixture.
Pour in the water.
Cover the skillet and cook over medium-low heat for 15 minutes.
Remove the lid and stir often while it cooks uncovered.
Cook until the mixture turns dry and the lamb develops a dark roasted coating.
Add the green chilies, curry leaves, garam masala, and the remaining black pepper and stir constantly for 5 minutes.
Notes
Tips and Tricks
Brown the onions well - Take time with the onions. Their deep color gives the dish much of its rich taste.Do not overboil the lamb - Cook the lamb only until just tender during the first step. It will cook more later in the skillet.Keep stirring near the end - Once the liquid cooks off, stir often so the onions and spices do not burn.Adjust the black pepper last - Taste near the end and add more black pepper if you want a stronger pepper finish.Use a wide pan - A wider skillet helps the moisture cook off faster and gives the lamb more roasted edges.
Storing and Reheating
Reheat on stovetop - Place a serving in a saucepan with 1 to 2 tablespoons water. Warm over low heat, stirring until heated through.Refrigerate - Place leftovers in an airtight container and store in the refrigerator for up to 3 days.Freeze - Place the cooled lamb in a freezer-safe container and freeze for up to 2 months. Thaw in the refrigerator before reheating.