Melt butter. Add onions, and saute until wilted. Add mushrooms, saute until juice is rendered out.
Add dill, paprika, and mix well.
Add tamari, water, bring to a boil and reduce to a simmer.
In a large stockpot, make roux using butter and flour, cook 10 minutes. Drain some water from soup and beat into roux in stockpot until smooth. IMPORTANT- you will get flour lumps if you try to skip this step!
Add water-smoothed roux to kettle. Add milk and simmer until it thickens again, coating back of spoon. Turn off heat, beat in sour cream until well blended, then beat in salt and pepper.
Recipe courtesy of Old Wives Tale, Portland