Marinated flank steak with blue cheese sauce

Ingredients:

• 550 g beef flank steak
• 2 tbsp. l. olive oil
• 1 tbsp balsamic vinegar
• 1 tsp. brown sugar
• 2 cloves garlic, crushed
• 2 tablespoons crumbled blue cheese
• 2 tbsp. low-fat yogurt or kefir
• A little Worcestershire sauce
• 1 medium red onion
• 0.5 tsp salt
• 1/4 tsp ground black pepper
• 12 radicchio leaves
• 2 tbsp chopped parsley leaves

Preparation:

1. Place the steak between 2 pieces of plastic wrap or parchment paper and pound to a thickness of 0.5 cm. Cut diagonally against the grain into 4 equal pieces.
2. In a small bowl, combine 1 tablespoon of olive oil, balsamic vinegar, sugar, and garlic. Place the steak in a resealable plastic bag, pour the marinade over it, and let it marinate for 30 minutes at room temperature or for 1 hour in the refrigerator.
3. Meanwhile, in a small bowl, combine the blue cheese and buttermilk. Mash with a fork until creamy. Stir in the Worcestershire sauce.
4. Spray a large grill pan with cooking spray and heat over medium-high heat. Slice the onion into 0.5 cm (1/4 inch) rounds, brush both sides with the remaining 1 tablespoon of olive oil, and grill for 6 minutes per side. Then separate into rings.
5. Remove the meat from the marinade and season both sides with salt and pepper. Discard the marinade. Grill the meat over medium-high heat for about 3 minutes per side for medium-rare.
6. Arrange 3 radicchio leaves and a handful of onions on each plate. Top with a piece of steak. Drizzle with blue cheese sauce and sprinkle with parsley.