Bring water to a boil and salt it for the pasta.
Place the porcini mushrooms in a small pot with stock and bring to a simmer. Steep until mushrooms are tender.
In a deep skillet, heat the EVOO over medium-high heat. Add the portobellos, shiitakes, garlic, shallots, thyme, allspice and black pepper. Cook for 10-12 minutes, until dark and tender.
Remove half of the mushrooms and place in food processor. Draw off a cup of the mushroom-stock broth and add to the processor. Grind the mushrooms into a thick sauce and add back to the skillet.
Remove the porcinis with a slotted spoon, chop and add to the skillet. Ladle in the stock, but do not add the last few spoonfuls at the bottom of the pot. Discard this liquid, as any grit in the dried mushrooms will have settled here. Season the sauce with salt, to taste. Remove the thyme stems.
Drain pasta when it still has a nice bite to it and add it to the mushroom sauce to absorb the flavor. Toss with arugula to wilt in. Adjust seasonings and top bowlfuls with nuts and cheese and a drizzle of truffle oil if you want to go into true ‘Shroom Madness!