Here's a step-by-step recipe for making Chicken Dum Biryani at home:

Ingredients:
For the Chicken Marinade:
500 grams chicken (cut into pieces)
1 cup yogurt
1 tablespoon ginger-garlic paste
1 teaspoon turmeric powder
1 teaspoon red chili powder
1 teaspoon garam masala powder
1 teaspoon coriander powder
Salt to taste
2 tablespoons lemon juice
For the Rice:
2 cups basmati rice
4 cups water
2-3 green cardamom pods
2-3 cloves
1-inch cinnamon stick
1 bay leaf
Salt to taste
For the Biryani:
2 large onions (thinly sliced)
3-4 green chilies (slit)
1 teaspoon cumin seeds
2 tablespoons ghee or oil
1/4 cup fresh coriander leaves (chopped)
1/4 cup fresh mint leaves (chopped)
1 teaspoon saffron strands (soaked in 2 tablespoons warm milk)
1/4 cup fried onions (optional, for garnish)

Instructions:
Step 1: Marinate the Chicken
Combine the yogurt, ginger-garlic paste, turmeric powder, red chili powder, garam masala powder, coriander powder, salt, and lemon juice in a large bowl.
Add the chicken pieces to the marinade, ensuring they are well coated.
Cover the bowl and refrigerate for at least 2 hours or overnight for best results.

Step 2: Prepare the Rice
Rinse the basmati rice under cold water until the water runs clear.
Bring the water to a boil in a large pot. Add the green cardamom pods, cloves, cinnamon sticks, bay leaf, and salt.
Add the rice to the boiling water and cook until it is 70% cooked (it should still have a bite).
Drain the rice and set aside.

Step 3: Cook the Chicken
Heat the ghee or oil in a large pan over medium heat.
Add the cumin seeds and let them splutter.
Add the sliced onions and green chilies. Cook until the onions are golden brown.
Add the marinated chicken to the pan. Cook until the chicken is 80% done (it will continue cooking during the dum process).

Step 4: Layer the Biryani
Start with a layer of partially cooked chicken at the bottom in a heavy-bottomed pot.
Add a layer of the partially cooked rice on top of the chicken.
Sprinkle a portion of the chopped coriander leaves and mint leaves over the rice.
Drizzle a portion of the saffron milk over the rice.
Repeat the layering process until all the chicken and rice are used up, ending with a layer of rice on top.
Cover the pot with a tight-fitting lid. If the lid isn't tight enough, seal it with dough or aluminum foil to prevent steam from escaping.

Step 5: Dum Cooking
Place the sealed pot on a tawa (griddle) or directly on low heat.
Cook for 20-25 minutes on low heat, allowing the flavors to meld together and the chicken to cook through completely.

Step 6: Serve
Once done, gently fluff the biryani with a fork to mix the layers.
Garnish with fried onions, and serve hot with raita or a side salad.