Grind the mushrooms and onion in your food grinder and then set aside (You can use you food processor if you don't have a food grinder).
Heat the oil in a large saucepan, over medium heat.
Add the mushroom and onion paste into the saucepan and sauté for another 10 minutes.
Add the rice (drained) along with an additional 1 cup of water. Stir and let the mixture boil for 10 minutes or until almost all excess liquid is absorbed. It doesn’t need to be cooked, it just has to absorb all of the excess water. Add spices.
Remove from heat and add chopped parsley. Let it cool for 10 minutes.
For the wrappers and assembly:
Separate the grape leaves and make the rolls adding about 1 Tablespoon of filling into each roll.
Take a large pot and line the bottom with some grape leaves.
Put the assembled rolls in the pan on top of the grape leaves. Arrange them around the pan until the pan is full.
Cover with remaining grape leaves.
Add water until all rolls are covered.
Place in oven at 392F˚ for 1 hour. Check every 20 minutes and add more water if necessary. 15 minutes before it’s ready, add the tomato paste and finish cooking.