Soak the dried mushrooms in 2/3 cup water for 2 hours. Remove mushrooms and chop fine. Reserve soaking liquid and set aside. Melt 4 tablespoons butter in a large skillet. Saute onions over medium heat stirring occasionally until nicely browned about 25 minutes. Meanwhile in another skillet, melt 4 more tablespoons of butter and saute all the mushrooms until golden about 25 minutes. Add garlic and sour cream to the mushrooms and saute for 3 minutes. In saucepan, combine rice, water, mushroom liquid and remaining butter, bring to a boil. Add salt and pepper, reduce heat, cover and simmer until the rice has absorbed all the liquid about 20 minutes. Stir in mushrooms and onions and heat for about 5 minutes. Transfer to serving bowl, sprinkle with dill and serve.