Heat a large skillet over medium-high heat and add the butter or olive oil.
Add the chicken pieces, curry powder, and the sliced or chopped onion to the hot skillet; cook for about 3 minutes, stirring occasionally, until the chicken begins to brown.
Add the chopped garlic and jalapeños, then cook another 2 minutes, stirring so the garlic does not burn.
Pour in the coconut milk, then stir in the tamari (or soy sauce or fish sauce) and honey until combined.
Mix in the shredded kale or spinach and season with salt and black pepper; reduce heat to medium and simmer 5–10 minutes until the chicken is cooked through and the greens are wilted.
Stir in the fresh basil, lime juice, and roasted cashews (if using) just before serving.
Serve the coconut curry basil chicken over steamed rice with extra basil or lime if desired.