Bring a large pot of water to a boil, salt it, add the pasta and cook until al dente. Drain.
While the pasta is working, in a saucepan, simmer the vegetable stock and porcinis until the porcinis are softened, 15 minutes.
In a medium saucepan, melt the butter over medium heat. Stir in the shallots; season with salt and pepper. Cook, stirring frequently, until softened, 7 to 8 minutes. Stir in the parsley, then the wine. Lower the heat to low.
Remove the mushrooms from the stock and finely chop; add to the parsley-shallot mixture. Ladle in the stock up to the last ladleful (to avoid the grit at the bottom).
Toss the pasta with the porcini-parsley sauce and serve with a little grated pecorino romano on top.