Heat olive oil in large frying pan over medium heat. Add chicken and onions and cook, stirring occasionally, until onions are translucent and chicken is lightly cooked on all sides, about 8 minutes.
Add mushrooms, 1 cup chicken stock, paprika, soy sauce, dill, thyme, marjoram and black pepper. Simmer, stirring occasionally, until mushrooms soften and become dark in color, about 15 minutes.
Melt butter in large Dutch oven over medium heat. Whisk in flour and continue whisking while mixture cooks for another 3 minutes. Add milk and reduce heat to medium-low. Continue cooking, stirring once every minute or so, until mixture thickens, about 10 minutes.
Pour mushroom mixture into milk mixture. Stir in lemon juice and remaining 2 cups chicken stock. Cover and simmer over low heat for 20 minutes, until very fragrant with the smell of mushrooms.
Remove pan from the heat and watch the mixture until it stops simmering. When it ceases, stir in the sour cream. Add salt to taste and serve.