Using a food processor, crush the walnuts to form fine crumbs. if it's too thick, add 1/8 cup water then process again.
Heat vegetable oil in a medium sized pot over medium heat.
Saute onion for 5 minutes until light.
Add walnuts and saute onion and walnut for 5 minutes.
Add 2 cups of water. Turn the heat up to high and bring the mixture to boil, turn the heat down to medium so it simmers then add pumpkin, chicken thighs, salt and pepper and let it cook for 30 minutes.
After 30 minutes, check if the chicken is cooked. Once the chicken is cooked, add 1 cup pomegranate molasses and simmer for 10 minutes.
Take the chicken out of the stew and into a plate.
Add salt and pepper to taste. Let it simmer for another 10 more minutes until thickens. (If the stew is too thick, add some more water) Taste the stew, if it's not sour enough, add some more pomegranate molasses and if it's too sour, add 1 - 2 tbsp brown sugar.
Add the chicken thighs back into the stew and let it simmer over low heat for 15 minutes, stir every 5 minutes.
Serve warm with rice.