In a bowl, combine duck with half of the olive oil and next two ingredients. Cover and refrigerate for 2 hours. Heat remaining oil in a large skillet over medium-high heat. Add duck and quickly sear evenly, but only to rare doneness. Remove duck and add onion, garlic and asparagus. Cook for 3 – 4 minutes. Add mushrooms, broth and wine. Bring to a boil. Reduce heat and simmer for 3 – 4 minutes. Return duck to pan and stir in butter until melted. Top with blue cheese and serve.