In a heavy bottom soup pot or Dutch oven, melt the butter over medium heat and add the onions and shallots and saute for about 3 - 4 minutes, or until softened and translucent.
Next add the sliced mushrooms, salt and pepper
Turn up the heat to medium-high. Cook, stirring occasionally, until the mushrooms release their juices and start to brown slightly. This should take about 10 minutes or so.
Once the mushrooms are golden brown, turn the heat down to medium and add the minced garlic, stir and let cook for about 30 seconds and then add the 1/2 cup medium dry sherry to the pot to deglaze.
Once almost all of the sherry has evaporated, sprinkle on the flour and paprika, stir and let cook for about 1 minute.
Next, while stirring, add the stock or broth, the milk and the soy sauce and bring to a gentle boil, the reduce the heat and simmer for about 10 - 15 minutes, stirring occasionally
Remove from the heat and stir in the sour cream, fresh lemon juice and fresh dill
If using the optional miso, take a little broth out and stir in 1 tsp of mellow light white miso until it dissolves and add that back into the pot of soup
Taste for salt and pepper and adjust as needed.