Combine all marinade ingredients in a large bowl or storage container, cover, refrigerate several hours or overnight.
Preheat oven to 180°C.
Remove duck breasts from marinade, reserve marinade.
Cook duck breasts skin side down in a large fry pan until skin is browned and crispy and fat is rendered from skin.
In an oven proof dish pour enough of the reserved marinade, so that the liquid will come about half way up each breast, discard the rest. Place duck breasts flesh side down in marinade and cook in oven for 20-25 minutes.
Remove duck beasts and allow to rest for 5 minutes, slice thickly.
If desired which I do. Skim off any excess fat from the surface of liquid, place pan over stove and mix a little water with some cornflour, add this to the marinade and thicken, serve as extra sauce with duck.
For the Vegetables.
Combine miso, mirin, sake, sugar, vinegar and soy sauce in a saucepan and heat over a medium heat to dissolve sugar, remove from heat and set to one side.
Heat some oil in a wok or large frying pan, add all the vegetables and chili except the green onion, stir-fry 4-5 minutes until veg are just tender, you want them to still have a nice crunch.
Add dressing and onion and stir until heated through.
To Serve: Place a mound of the veg on a plate and top with sliced duck, drizzle with extra sauce and serve the rest on the side.