Argentine-Style Stuffed Flank Steak

INGREDIENTS

• 1 (1 1/2 lb) flank steaks, trimmed of excess fat and silver skin
• 1 tablespoon red wine vinegar
• 1 tablespoon paprika
• 2 tablespoons tomato paste
• 2 garlic cloves, minced
• 4 tablespoons olive oil
• 1/4 lb prosciutto, thinly sliced
• 1 bunch spinach, carefully washed and stemmed
• 1 carrot, peeled and grated
• 1/2 yellow onion, sliced
• 1 red bell pepper, roasted (peeled and sliced)
• 1 cup fresh basil leaf
• 1/2 cup dried breadcrumbs
• 1/2 cup grated pecorino romano cheese
• 2 teaspoons dried thyme
• salt and pepper, to taste
• 1/2 cup white wine
• 1/2 cup marsala
• 1 cup beef stock
• 1 tablespoon Worcestershire sauce