Place the curry leaves, ginger, lemongrass paste (if using), cilantro, jalapeño or serrano pepper (if using), and 3 tablespoons of water in the bowl of a food processor. Puree into a nearly smooth paste. Set aside.
For the curry:
3 tablespoons canola oil
1 1/2 teaspoons cumin seeds
1 teaspoon brown mustard seeds
15 fresh or 22 frozen curry leaves, roughly chopped
3 dried red chile peppers (omit for milder flavor)
1 teaspoon ground turmeric powder
1 1/2 pounds (around 4 cups chopped) green beans, cut on bias into 1/2 -inch pieces
2 (13.5-ounce) cans coconut milk
1/2 cup heavy cream or half-and-half
1 teaspoon kosher salt
2 pounds local or sustainably caught shrimp (16 to 20 shrimp, or fewer if you wish), peeled and deveined
1/4 cup finely chopped cilantro
1. Heat the oil, cumin seeds, and mustard seeds in a large pot over medium-high heat. Cook, stirring occasionally, until the cumin seeds brown and become fragrant and the mustard seeds pop (1 to 2 minutes).
2. Add the curry leaves, chile peppers, and turmeric, and cook, stirring, for 1 minute.
3. Stir in the herb paste, reduce heat to low, and cook until the mixture is very fragrant (2 to 3 minutes).
4. Add the green beans and cook for 4 to 6 minutes. Add a tablespoon or two of water if the pan gets too dry while you cook the beans. Make sure the beans are cooking without burning the herbs.
5. Pour in the coconut milk and the cream. Stir, increase heat to high, and bring to a boil. Reduce the heat to medium-low and stir in the salt.
6. Add the shrimp and simmer until the shrimp curl and are just cooked through (2 to 4 minutes), stirring occasionally. Stir in the cilantro and serve.
Makes 8 servings