For the bean puree:

1. Drain and rinse the beans, place in a medium pot, and add enough water to cover by about 2 inches. Add the bay leaf, garlic, and 1/2 teaspoon salt. Cover with a lid and bring to a boil. Then reduce the heat to low and continue cooking with the lid ajar – the water should be simmering very gently –  until the beans are cooked through and creamy, 40 to 60 minutes.
2. Turn the heat off and stir in 2 teaspoons salt into the pot. Let stand for 10 more minutes for the beans to absorb the salt.
3. Reserve about 1/2 cup of the bean cooking water, then drain the beans. Discard the bay leaf.
4. Transfer beans to a food processor along with 1/3 cup of the bean cooking water, lemon juice, oil, and black pepper. (If all the beans don’t fit, puree in 2 batches). Puree until completely smooth, adding more bean water if you want a creamier consistency. Taste and season with more salt or lemon juice, if needed.

For the mushrooms:

1. While the beans cook, wipe the mushrooms clean with a damp paper towel. Slice creminis and shiitakes, and tear oyster and maitake mushrooms into bite-size strips with your hands.
2. Heat 2 tablespoons oil in a large non-stick skillet over medium-high heat. Add half of the mushrooms with 1/4 teaspoon salt and pepper. Cook until they’re softened and golden brown, 8 to 10 minutes. In the last 30 seconds of cooking, stir in half of the crushed garlic. 
3. Transfer the mushrooms to a plate and sprinkle with half of the parsley. Cook the remaining mushrooms the same way and combine them all together.
4. Serve the puree topped with the mushrooms.