Measure, wash and soak basmati rice. Let it soak for 30 minutes before cooking.
Cut Fish fillets into 3/4 inch or medium size pieces.
In a medium sized bowl, beat yogurt to get a smooth consistency. Then add all ingredients for marination and mix well.
Add the fish pieces to this marinade. Mix well so that the marinade coats fish well. Let it marinate for 30 minutes.
In the meantime, in a pan, heat ghee. Add sliced onions and fry until they turn golden brown or caramelized. Remove from pan and drain into a bounty to remove excess ghee.
While the onions are caramelizing, wash, chop and keep aside cilantro & mint.
Prep the nuts. If you'd like, you can add some raisins as well.
Heat milk and saffron in a small bowl. For convenience, use a microwave. Else, heat milk in a small saucepan and add saffron. Bring it to a boil and remove from heat. Keep aside.
Cooking the fish
30 minutes into marination, pan fry fish pieces in the same pan that was used to caramelize onions. You can add a tbsp of cooking oil if desired or use left over ghee.
Only pan fry the fish pieces. 2 minutes each side is good enough. Keep aside the marination gravy. This will be used later.
Cooking Rice
In a large pot, bring around 5 cups of water to a boil. When the water is hot, add the spices listed under 'For Rice'. Get it to a boil and add rice.
Gently stir with a spoon occasionally while the rice is cooking. Don't reduce the flame.
Just when the rice is about 75% cooked (the rice grains should have a slight bite to them), drain the rice in a colander. Gently fluff and keep aside.
Layering & cooking
While the rice is cooking, preheat oven to 180 degrees Celsius or 360 degree Fahrenheit.
Grease a thick bottom oven safe pan/ disposable aluminum tray with ghee or cooking oil.
Let's begin layering. Layer half of pan fried fish and sprinkle half of chopped mint, cilantro and nuts. Next layer half of the 75% cooked rice.
Sprinkle half of caramelized onions, green chili, saffron milk, almonds and cashew nuts.
Layer the remaining pan fried fish.
Layer the remaining rice and sprinkle the remaining fried onions, green chili, cilantro, mint, saffron milk, almonds and cashew nuts. Also add the left over marination gravy.
You can make 2 layers of fish and rice or 4 layers. Or more than that (depends on the depth of the container and the quantity you are cooking). But the top most layer should always be that of rice.
Seal the container with an aluminum foil. Bake the biryani for 20-25 minutes.
Remove from oven. Serve hot and delicately flavored biryani with 'Dahi Ki Chutney' and 'Mirchi Ka Salan'. Enjoy!
Notes
The nutritional value is for 1 Serving. Please keep in mind that the nutrition value is a rough estimate and can vary based on the product used.