Source: Cindy5_NY - original recipe from The EatingWell Healthy in a Hurry Cookbook
adapted by There's Always Thyme to Cook
2 teaspoons plus 1 tablespoon canola oil, divided
1 pound flank steak, trimmed
1 pound cremini mushrooms, cleaned, stemmed and thinly sliced
1 large onion, sliced
3/4 teaspoon dried thyme
1/2 teaspoon salt
1/2 teaspoon freshly ground pepper
3 tablespoons all-purpose flour
1 14-ounce can reduced-sodium beef broth
2 tablespoons cognac, or brandy
1 tablespoon red-wine vinegar
1/2 cup reduced-fat sour cream (I used regular sour cream)
4 tablespoons chopped fresh chives, or parsley
Heat 2 teaspoons oil in a large skillet over high heat until shimmering but not smoking. Add steak and cook until browned on both sides, 3 to 4 minutes per side. (The meat will be rare, but will continue to cook as it rests.) Transfer to a cutting board and let rest for 5 minutes. Cut lengthwise into 2 long pieces then crosswise, across the grain, into 1/4-inch-thick slices.
Heat the remaining 1 tablespoon oil in the pan over medium heat. Add mushrooms, onion, thyme, salt and pepper and cook, stirring often, until the vegetables are very tender and lightly browned, 8 to 12 minutes. Sprinkle flour over the vegetables; stir to coat. Stir in the broth, cognac (or brandy) and vinegar and bring to a boil, stirring often. Reduce heat to a simmer, and continue cooking, stirring often, until the mixture is thickened, about 3 minutes. Stir in sour cream, chives (or parsley), the sliced steak and any accumulated juices. Bring to a simmer and cook, stirring, until heated through, 1 to 2 minutes more.
Serve with egg noodles or mashed potatoes!