heat a pan to very hot & place duck breast skin side down without any oil & press down firmly so it doesn't curl up on edges; cook for 4-5 mins till skin is brown & crispy, turn & cook for further 3 mins.
Take pan off the stove & place in the pre-heated oven for approx. 8 mins.
Meanwhile in another pan sauté garlic, onions & ginger in the sesame oil on a moderate heat until softened. Take off the heat, then pour water & stock into saucepan & add the noodles & heat through on med heat.
Take duck from oven and rest for 10 mins loosely covered with foil.
Put sautéed onions etc back on heat then add carrot & bok choy stir-fry 2mins;add cashews then transfer to plate retaining pan juices.
Slice duck and place on top of vegetables then mix the arrowroot & water, ad to pan on med heat till thickened and pour over finished dish.