Roast rice in a small dry skillet over medium heat, shaking the pan frequently, until the grains are a light golden brown, about 5 minutes. Transfer to a plate to cool. Add all spices to the skillet except turmeric and roast over medium heat, shaking the pan, until toasted and fragrant, about 3 minutes. Transfer the spices to the plate. Grind the rice and roasted spices in a spice mill or blender into a fine powder. Work in turmeric. Store the powder in an airtight container away from heat and light. It will keep for several months.
Heat oil and butter in a large saucepan. Stir in the chicken and colombo powder (4 tbs per 2 lbs chicken). Cook over medium heat for 15 minutes, until brown.
Add broth, onions 1/2 of the milk, garlic, lime juice, thyme, chives, parsley, pepper, salt and pepper. Simmer over medium heat for 45 minutes.
Turn off heat and stir in remaining coconut milk, bananas and pistachios.