1. Trim any fat or sinew off the meat and cut into thin strips. Place meat in a mixing bowl with garlic, cardamom, and pepper, and marinate for 15 minutes.

2. Combine yogurt, mustard, cognac, and flour in a bowl and whisk until smooth.

3. Heat the oil in a large nonstick frying pan. Cook the onions over medium-low heat until a deep golden brown, stirring often. Add the sugar after 5 minutes.

4. Just before serving, season the beef with salt and pepper. Increase the heat to high, add the beef to the onions, and saute for 1 to 2 minutes, or until cooked to taste. Stir in the yogurt mixture and bring to a boil. Add salt and pepper to taste. Sprinkle the beef with the chives and serve at once.