Heat a Dutch oven or large pot over medium high to high heat. Coat the bottom of the pan with oil. Season your lamb on all sides with salt and pepper. When the oil is hot, sear the lamb in batches until they develop a nice brown crust on all sides. Remove the lamb from the pot.
Lower the heat to medium and add enough oil to coat the pot. Add all of the spices from turmeric to cumin. Cook the spices until the oil becomes fragrant, about a minute. Add the onions and soften for 2 minutes. Use a rubber spatula to scrape up all of the delicious bits at the bottom of the pot, there’s a lot of flavor there!
While the onions soften, create a paste from the garlic, jalapeno, cilantro, and ginger using either a mortar and pestle or food processor. Add salt to the paste to extract more moisture. Add the paste to the pot and mix well.
Add the lamb back to the pot and stir everything together. Add 2 cans of coconut milk and enough water to cover everything in the pot. Cover the pot and increase the heat to medium high to bring the curry to a boil.
Once the curry starts to boil, lower the heat to low. Taste the curry and season with salt to your liking. Be careful not to over-salt at this stage because the flavors will develop over time. It’s better to add more salt later. Mix flour in about half a cup of cold water to dissolve and then add it to the curry to thicken the broth. If you like your curry thicker, dissolve more flour and add it to the pot.
Continue simmering for at least 2 hours until the meat is very tender. Taste the curry and add more salt if necessary.