Bring a large pot of water to a boil. Salt it, add the pasta and cook to al dente. Drain.
While the pasta is working, in a saucepan, simmer the vegetable stock and porcinis until the mushrooms have softened, 15 minutes.
In a medium saucepan, melt the butter over medium heat. Stir in the shallots and season with salt and pepper. Cook, stirring frequently, until softened, 7-8 minutes. Add the wine and reduce heat to low.
Remove the mushrooms from the stock and finely chop. Add them to the parsley-shallot mixture. Ladle in the stock, leaving some behind to avoid the grit at the bottom of the saucepan.
Toss the pasta with the porcini sauce and parsley. Serve with a little grated Pecorino Romano on top.