Using a sharp knife cut fish into two equal pieces and lightly score the skin.
In a pot, boil water add a pinch of water, add in the asparagus and boil for minute. Transfer to ice bath and allow to cool.
In a bowl, place onion, add asparagus, onion, radishes, mint, balsamic vinegar, lemon juice and 3 tablespoons olive oil. Season with salt and pepper, mix well and refrigerate.
Heat 2 tablespoons oil in a large nonstick skillet over medium-high heat. Season fish with salt and pepper and cook, skin side down, until skin is golden brown and crisp, about 5 minutes. Turn fish and cook for 2 minutes; then deglaze the pan with white wine and vinegar and continue to cook for another minute until fish is opaque.
Divide asparagus salad between two plates and top with fish along with pan juices.