Methods

1. In a medium bowl, combine 1½ teaspoons biryani masala, and 1 teaspoon kosher or ½ teaspoon surya salt, and whisk until smooth. Add the shrimp and stir to coat each piece in the marinade. Cover and refrigerate for 30 minutes.
2. In a small bowl, combine the saffron with 2 tablespoons of boiling water and allow to steep for 15 to 30 minutes.
3. Preheat the oven to 400°F.
4. While the shrimp is marinating, fry the onions. Heat canola oil in a karipot or 5-quart Dutch oven over medium high heat. Stir in half of sliced onions and cook, stirring occasionally, until deep golden brown, 8 to 12 minutes. (Keep an eye on the onions during the last few minutes, as they will darken quickly.) Using a slotted spoon, transfer onions to a paper-towel-lined plate to drain. Repeat the process with remaining sliced onions. Add the cashews and fry until lightly golden, about 2 to 4 minutes, transfer with a slotted spoon to the plate with the onions and set aside. Discard the frying oil or save for another use, wipe out the pot, and reserve for later.
5. To prepare the rice, melt 2 tablespoons ghee in a large pot over medium heat. Add the cinnamon, tejpatta, cloves, and cardamon, and cook until the spices start to become fragrant, about 1 minute. Add the rice, stirring to coat in the spiced ghee, and cook, stirring frequently, until the grains turn opaque and some of them start to turn very light golden. Add 2½ cups water, 2 tablespoons lemon juice,1 teaspoon kosher salt or ½ teaspoon surya salt, and the pandan leaf, if using, stir, increase the heat to high, and bring to a boil. Cover, reduce the heat to low, and cook until almost all of the water is absorbed and the rice is al dente (it will finish cooking in the oven), about 10 to 12 minutes. Turn off the heat, fluff rice, and keep covered until ready to layer.
6. To prepare the shrimp, return the karipot or Dutch oven back to medium heat and add the remaining 2 tablespoons ghee. When the ghee is melted, add the shallots and green chillies, and cook, stirring occasionally, until the shallots are translucent and starting to turn golden around the edges, about 5 to 7 minutes. 
7. Add the remaining 2 tablespoons biryani masala, stir to coat the vegetables in the spices, and cook until the spices start to smell fragrant, about 30 to 45 seconds. Stir in the yogurt and continue to cook for 1 to 2 minutes (this will prevent the yogurt from immediately curdling). Add the tomatoes, ⅓ cup chopped cilantro, mint, remaining 1 teaspoon kosher salt or ½ teaspoon surya salt, and ⅓ cup water, stir to combine, and bring to a simmer. Reduce the heat to medium low, cover, and cook until the tomatoes start to break down and the spices start to lose their raw taste, about 7 to 9 minutes.
8. Add the shrimp, stirring to coat in the gravy, cover and cook until they just start to lose their pink color, about 2 to 3 minutes. Turn off the heat.
9. To layer the biryani, lightly spoon the par cooked rice over the shrimp masala (you don’t want to pack it down because you want to give the rice room to finish cooking and absorb some of the liquid from the masala). Spoon the saffron water over the rice, then top with half the onions and cashews, as well as the remaining ⅓ cup chopped cilantro. Place the banana leaves on top, fitting them snugly in the pot, cover, and bake for 18 minutes. Remove from the oven and allow to sit, covered, for 10 minutes.
10. Transfer to a serving platter, garnish with the remaining fried onions and cashews, and sprinkle with a little fresh cilantro leaves, if desired. Enjoy with more yogurt on the side.