Melt butter in a large skillet over medium heat. Add porcini mushrooms, onion, garlic, and parsley; cook and stir until golden brown, 5 to 8 minutes. Add sausage; cook and stir until browned, about 2 minutes.
Pour white wine into the skillet and simmer, scraping up the browned bits off the bottom of the skillet, until most of the wine evaporates, about 3 minutes. Pour in vegetable broth; cook and stir until sauce reduces, about 5 minutes. Stir in heavy cream, salt, and pepper.
Fill a large pot with lightly salted water and bring to a rolling boil. Stir in tagliatelle, bring back to a boil, and cook until tender yet firm to the bite, about 8 minutes.
Drain tagliatelle and stir into the sauce in the skillet. Stir in Parmigiano cheese. Divide tagliatelle among 4 serving plates and garnish with toasted almonds.