2 teaspoons canola oil, divided
1 pound flank steak, trimmed
4 large portobello mushrooms, stemmed, halved and thinly sliced
1 large onion, sliced
3/4 teaspoon dried thyme
1/2 teaspoon salt
1/2 teaspoon freshly ground pepper
3 tablespoon all-purpose flour
1 14-ounce c reduced-sodium beef broth
2 tablespoon cognac, or brandy
1 tablespoon red-wine vinegar
1/2 cup reduced-fat sour cream
4 tablespoon chopped fresh chives, or parsley