1) Bring a large pan of salted water to a boil over high heat. Add the noodles and stir to keep them from sticking together. Cook until barely tender and still firm, 3 to 4 minutes.
2) Drain immediately and rinse under cold running water to cool. Drain the noodles really well, transfer to a wide serving bowl, and, so they don't stick together, toss immediately 45ml of the sesame oil.
Meanwhile, make the sauce:
1) In a saucepan, heat 60ml sesame oil over medium-low heat. Add the ginger, garlic, and chilli. Cook, stirring for a minute, until the vegetables are soft and fragrant.
2) Place into a blender along with the brown sugar, peanut butter, vinegar, soy sauce, water, chilli sauce, and the remaining 30ml sesame oil. Puree and refrigerate until cold.
3) Toast the sesame seeds in a dry non-stick frying pan, over medium-low heat, until golden brown. (Shake the pan constantly to keep the seeds from burning).
Next prepare the pears and duck:
1) Preheat the oven to 180C/Gas 4.
2) Put the pears on a baking sheet, cut sides up, sprinkle with salt and pepper and drizzle with 1 tablespoon sesame oil. Place in the oven and roast for 15 to 20 minutes, until very tender when pierced with a skewer.
3) Meanwhile, place the duck breasts on a cutting board skin side up and score all over in a crosshatch pattern, so the fat will render and the skin will crisp. Season all over with salt and pepper and drizzle with 1 tablespoon sesame oil.
4) Put the breasts into a stainless steel pan over a medium heat, skin side down, and cook slowly for about 12 to 15 minutes, until the fat is rendered and the skin is browned and crispy, occasionally spooning the excess fat out into a bowl. Turn the breasts and cook for 1 to 2 more minutes for medium-rare.
5) Remove from the heat and transfer the duck to a cutting board to rest.
1) Put the noodles into a serving bowl and toss with the sesame sauce.
2) Divide the noodles evenly between 4 bowls. Sprinkle with the sesame seeds and green onions, and garnish with the lime wedges.
3) Cut each duck breast crosswise, on an angle, into 8 slices. Add half a sliced duck breast and a pear to each bowl and garnish with watercress.