Mushroom soup

This month's issue of Fine Cooking had a terrific looking recipe for mushroom soup. However I didn't completely remember the ingredients when I went shopping. No matter, what came out was another "We can serve this to people" accolade from Madame.
What did I do wrong? I was convinced that the recipe said to use dashi - that stock used in Japanese cooking, made from kombu (kelp) and dried bonito flakes. After all, there would be lots of umami resulting from this. I thought it would be interesting to make my own dashi, so I followed Alton Brown's recipe for that.
The recipe actually called for chicken stock. Never mind! I also used more mushrooms than the recipe called for. I did follow the technique carefully - because it seemed unusual to me. I am glad that I did because the result was outstanding.

Ingredients

4t unsalted butter (divided use)

1T olive oil

1t whole cumin seeds

1/2 lb white mushrooms, coarsely chopped

1/2 lb cremini mushrooms, coarsely chopped

6oz oyster mushrooms, coarsely chopped

1/2 cup Negro Modelo beer (or other dark/brown beer)

3 large leeks, white and light green parts only, sliced into thin rounds

2 cloves garlic, minced. 

2 cups dashi + 2 cups water warmed to a low simmer

2 t habanero vodka or other hot sauce

1/4 cup heavy cream

salt/pepper to taste

Torn cilantro leaves as garnish

1/2 t sherry vinegar per serving

Method - and this is where Fine Cooking really shone

Melt 2 t of the butter + the oil in a 6qt pot on low/medium heat. I used the trusty Le Creuset for this and it worked well. When the butter is melted, add the cumin and cook until they brown a little. They should start to become fragrant and nutty. Take care not to burn the butter. 

Add all the mushrooms, turning the meat up to medium high. Cook the mushrooms until they become quite dry. The recipe said 8 - 10 minutes. Mine was more like 12 minutes.

Add the beer and continue to cook until dry.

Add the remaining butter and the leeks, cooking the leaks until soft. when the leeks are soft, add the garlic and cook a while longer - until the garlic is fragrant.

Turn the heat off and add the dashi and hot sauce. Stir and blend (taking care to put a kitchen towel over the blender goblet)  in batches until silky smooth and thick. Return the blended mixture to the original (but now cleaned) pot. Stir in the cream. Over low heat, bring the mixture up to a slow simmer. Adjust the seasoning.

Serve in warmed soup bowls with some drops of sherry vinegar and a few cilantro leaves on top.