Cook tagliatelle according to package directions, until al dente. Drain; set aside.
Melt butter in large skillet on medium heat. Add mushrooms, garlic and shallots; cook until mushrooms are golden brown, about 6 to 8 minutes. Add wine and thyme. Bring to boil and cook about 6 minutes until almost no liquid remains in skillet. Stir in heavy cream, White Summer Truffle Salt and black pepper. Reduce heat and simmer until thickened, about 10 to 12 minutes.
Remove thyme sprigs. Stir in cooked pasta; toss gently to coat. Garnish with additional White Summer Truffle Salt and grated Pecorino Romano cheese, if desired.