In a large pot, bring 2 quarts water to a boil along with 2 teaspoons salt, and cook pasta until al dente. Save 1 cup hot pasta water, when draining.
At the same time, heat the olive oil in a large sauté pan over medium heat. Add the mushrooms, season with salt and pepper, and saute, lowering heat to medium-low heat until tender, golden, and slightly crispy. Set the mushrooms aside.
Once you’ve drained the pasta, to the same pot, add 2 tablespoons butter and melt over medium-low heat letting it brown just a little. Add the garlic, shallots and black pepper, and saute over low heat until golden and fragrant- a little crispy here is nice! Whisk in the hot, salted pasta water and miso paste, whisking well, heating, but not boiling. Whisk in the cheese until it melts into the sauce and is creamy. Place the cooked pasta into the creamy miso sauce and toss well. Taste and adjust salt, pepper, and cheese to your liking. Either toss in the mushrooms with the pasta, or serve them on top of each bowl.
Divide among bowls and garnish with any of the options.
