In a small bowl, cover dried mushrooms with warm water. Soak for 25 minutes, or until softened.
Drain the mushrooms, and discard the soaking water. Chop finely.Bring a large pot of water to a boil.
Add farro, and cook for 10 minutes, stirring occasionally.
Drain and reserve.In a large skillet, over medium heat, heat the olive oil, and add onion, garlic, thyme, and mushrooms.Cook, stirring occasionally, for 5 minutes or until onions are tender.Stir in 2 tablespoons of sherry vinegar, and continue cooking for 1 minute.
Add chicken stock, and bring it to a boil.Stir in farro, and return to a boil.Lower the heat to a simmer, and cover with a tight fitting lid. Cook for 10 minutes.
Add asparagus, and cook, covered, for an additional 10 minutes.Season with 1 tablespoon sherry vinegar, salt and pepper.