Prepare the ingredients: Rinse the chicken breasts in running water, pat them dry with a kitchen towel, and cut them into half-inch cubes. Slice the onion and garlic and set them aside.
Grind the nuts: Use a mixer or blender to grind the walnuts and almonds until they are delicate and smooth. Transfer the ground nuts to a bowl, add three tablespoons of water, and stir to mix.
Sauté the aromatics: Add the olive oil, onion, and garlic to a preheated pot on medium-high heat. Cook the aromatics for three minutes while stirring occasionally. When the garlic and onion begin to brown, add the sliced chicken and stir to mix. After adding the chicken, lower the temperature to medium-low heat.
Add the ground nuts: Add the ground nuts, cardamom powder, nutmeg powder, salt, and pepper to the pot, and thoroughly mix all the ingredients. Add a quarter cup of water if the mixture is gloopy and thick.
Add pomegranate concentrate: Pour the pomegranate molasses and the rest of the water into the pot, and then stir to mix. Cook the Fesenjan for 35 minutes with the lid closed. When the Fesenjan is ready, garnish with parsley and serve with saffron rice.