In a large saucepan, saute onions and garlic in 1 Tbsp butter until onion is transparent, salt lightly. Add mushrooms, 1 tsp dill, beef stock, soy sauce, and paprika. Cover and simmer 15 minutes.
Melt remaining butter in another small saucepan. Whisk in flour and cook, whisking for several minutes. Add cream or half and half. Cook over low heat, about 10 minutes, stirring frequently until thick.
Stir the thickened cream into the mushroom and stock mixture. Cover and simmer 10 - 15 minutes.
Just before serving, add salt, pepper, lemon juice and sour cream.