In 12-inch nonstick skillet, melt butter over medium heat. Cook onions, bell pepper and mushrooms in butter 3 to 4 minutes, stirring occasionally, until tender. Remove from skillet to plate.
In small bowl, stir kasha and egg, coating well. Cook kasha in same skillet over medium heat about 3 minutes, stirring constantly, until browned and dry.
Return vegetables to skillet with kasha; stir in broth, salt and pepper. Heat to boiling; reduce heat to low. Cover and simmer 10 to 15 minutes or until broth is absorbed and kasha is tender.
Meanwhile, cook and drain pasta as directed on package. Stir cooked pasta and parsley into kasha mixture.