Toast the coriander and cumin seeds in a dry skillet over medium-high heat until they start to crackle, about 3 minutes; then cool slightly.
Grind the toasted seeds in a spice or coffee grinder until fine.
In a large bowl, combine the ground seeds, turmeric, 1/2 teaspoon kosher salt, a few grinds of black pepper, cayenne, curry powder, and olive oil; stir to form a paste.
Add the chicken pieces to the spice paste and stir to coat evenly; cover and refrigerate for at least 1 hour or overnight.
In a sauté pan over high heat, melt the butter, then add the chopped onion and cook until softened, about 4 minutes.
Add the minced garlic, chopped ginger, chopped jalapeño, bay leaves, and star anise; continue to sauté until the onion is lightly golden, about 5–7 minutes.
Add the coated chicken to the pan and cook until the pieces are opaque, about 5 minutes.
Stir in the chopped tomatoes and cook, stirring occasionally, until they soften, about 2 minutes.
Pour in the coconut milk and add 1/2 teaspoon salt; bring to a gentle boil, then reduce heat to low and simmer until the chicken is very tender, about 20 minutes.
Stir in the lemon juice and simmer for 5 more minutes.
Remove and discard the bay leaves and star anise, then transfer the curry to a serving bowl and top with chopped cashews and cilantro.
To prepare the basmati rice: place 1 cup rice in a large bowl, fill with room-temperature water, swirl by hand and drain; repeat washing until the water runs clear (3–4 times).
Refill the bowl with water and soak the rice for 30 minutes, then drain.
Bring 1 3/4 cups water and a pinch of salt to a boil in a medium saucepan, add the drained rice, stir, wait until it returns to a full boil, then reduce heat to the lowest setting, cover, and cook 15 minutes.
Fluff the rice with a fork and serve alongside the chicken curry.
Note: star anise is available at many supermarkets, specialty gourmet markets, or Asian markets.