Place potato in a large, deep frying pan and cover with cold water. Bring to the boil over high heat, then reduce heat to low and simmer for 7 minutes. Add asparagus and cook for 2 minutes. Drain and transfer to a large bowl of iced water. Cool. Drain.
Meanwhile, whisk 1/3 cup oil, lemon juice, maple syrup, wasabi paste and salt and pepper in a large bowl. Add potato, asparagus, rocket, pear and walnuts. Toss gently to combine.
Heat a large non-stick frying pan over medium-high heat. Add remaining oil to pan. Season salmon and add to pan, skin-side down, and cook for 2-3 minutes or until flesh turns opaque about two-thirds of the way up the side. Turn over and cook for a further 1-2 minutes for medium-rare, or until flesh is opaque all the way through. Serve with salad, parsley and lemon wedges.