I haven't made a recipe from Ad Hoc at Home in awhile, but it is a great Keller cookbook, so I decided to give another one of his soups a try. I wasn't exactly sure how I felt about mushroom stoup, but this soup, made with a homemade mushroom stock, was an absolutely wonderful vegetarian soup, and a nice, healthy soup. Surprisingly, making mushroom stock is actually quite easy and far less time-intensive than making a homemade chicken stock. The soup itself calls for Hen of the Woods mushrooms. There are no other mushrooms quite like these - they are extremely flavorful, funny looking and fantastic. I've cooked with them before when I got them at Wegmans, but this time I couldn't get my hands on them in time. It's Ok though, because just as Keller suggests in the book, oyster mushrooms are a perfectly reasonable substitute.
Thomas's Keller's Mushroom stock from Ad Hoc at Home (this is 1/2 of the original recipe)
2 lbs button mushrooms
1 medium onion, coarsely chopped
1 large carrot, chopped
greens from one leek, chopped
3 quarts of cold water
1/4 head of garlic, crushed, skin left on
1/4 bunch flat parsley
1/4 bunch thyme
2 bay leaves
1/2 T black peppercorns
Keller suggests pureeing some of the vegetables (specifically the mushrooms), but I decided not to do that, and just left them as is in the soup. It worked out fine and the broth had a fantastic mushroom flavor that soaked it up from the mushrooms. Put all of the vegetables in a stockpot and add the water, then bringing to a boil. Add the garlic, herbs, bay leaves and peppercorns and put the pot on simmer. Simmer uncovered for 45 minutes. Then, strain the soup, keeping only the stock. Keller suggests doing this using an ice bath, but you don't really need that either. Measure the stock. If you have more than two quarts, reduce it in a saucepan, simmering. The mushroom soup recipe on page 119 of Ad Hoc at home (see below) requires eight cups (two quarts) of the mushrooms stock, which is why I cut the recipe in half.
Thomas Keller's Mushroom Soup from Ad Hoc at Home
1 cup diced carrots
1 cup diced leeks
1 cup diced onion
1 1.2 tsp minced garlic
1 small bunch of tuscan kale (cavolo nero)
1 1/4 pounds (2 or 3 large) yukon gold potatoes
1 sachet (1 bay leaf, three sprigs of thyme, 10 black peppercorns and 1 clove garlic)
2/3 lb hen of the woods or oyster mushrooms
1 1/2 T butter
1/4 cups minced shallots
1 T fresh thyme
8 cups homemade mushroom stock
freshly ground black pepper
5 to 6 T garlic puree (I used five)
1 to 2 T red wine vinegar (I used one)
extra virgin olive oil
Heat three T of the canola oil in a large stockpot over medium heat. Add the carrots, leeks, onions and a pinch of salt. Cover with parchment paper and cook slowly for about 25 minutes. The vegetables will have released their liquid, Keller says, but will not yet be tender. Take off the parchment lid and add the garlic. Cook for another ten minutes until the carrots are tender. Remove the ribs from the kale and set aside for later.
Peel the potatoes and slice crosswise into large pieces, then quarter. Put the potatoes, herb sachet (which you can make using cheesecloth) and 2 tsp of salt in a saucepan. Simmer and cook until potatoes are tender, which took me about 15 minutes. Drain and allow to cool.
Add the mushroom stock to the stockpot with the carrots and other vegetables and bring to a simmer. Season with salt and pepper as needed. Blanch the kale in a large pot of salted water until just wilted and tender. Add the mushrooms, kale and potatoes to the pot, and add the vinegar at the end. Serve hot.