Heat 1 teaspoon of oil in a saucepan over medium heat. Stir in the chopped onion and cook until the onion turns translucent and the edges begin to brown, about 7 minutes. Scrape the onion into the container of a blender and set aside.
Return the saucepan to the stove and stir in the curry leaves and peppercorns. Cook and stir until the curry leaves wilt and turn almost dry, about 5 minutes. Stir in the coriander and cook 1 minute more. Scrape the curry leaves into the blender and pour in 1/2 cup of water. Blend until the mixture has turned into a coarse paste.
Heat 3 tablespoons of oil in the saucepan over medium heat. Stir in the sliced onions and cook until the onions have softened and turned translucent, about 5 minutes. Stir in the ginger and garlic, continue cooking until the garlic softens and mellows, about 3 minutes more. Stir in the cayenne pepper, salt and turmeric; continue cooking 2 minutes.
Finally, stir in the tomato paste, goat meat, pureed peppercorn sauce, and the remaining 1/2 cup of water. Bring to a simmer then reduce heat to medium-low, cover and simmer until the meat is tender, about 30 minutes.
I used this recipe with chopped larger chunks of goat with bone, from an Afghan (Halal) butcher - a much cheaper cut. I extended the final cook to 6 hours in a slow cooker. The result was very similar to curries we ate in Bangladesh. - 23 Apr 2016