In a heavy frying pan, toast the kasha, stirring until darkened slightly (2 - 3 minutes) over medium heat. Remove from heat.
In a large nonstick frying pan, heat the olive oil over medium heat. Add mushrooms and onion and saute until softened (3 - 5 minutes).
In a small saucepan, bring broth and water to a boil. Add to mushroom mixture and stir in kasha, thyme, and pepper. Reduce heat to low, cover and simmer until kasha is just tender but all liquid is absorbed (8 - 10 minutes).