For the duck marinade: In a medium bowl, add the ginger, peppercorns, rice wine, dark and light soy sauce, sea salt and star anise and stir to combine. Add the duck, cover with plastic wrap and leave to marinate for 30 minutes or as long as overnight in the refrigerator.
For the salsa: While the duck marinates, combine the cilantro, ginger, chile, grapefruit, lime juice and zest, pears, mangos, onions and chile flakes in a medium bowl. Toss to combine and season with sea salt. Set aside in the refrigerator until ready to serve.
Heat a wok or pan over high heat and add the vegetable oil. Place the duck into the wok, skin-side down, and fry until the skin is brown and crisp, 3 to 4 minutes. Flip the breasts and reduce the heat to medium. Cover and cook for 4 minutes.
Remove the duck and let rest for 5 minutes. Chop the duck into bite-size pieces, then dust the pieces in the cornstarch and coat well.
Heat a wok or pan over high heat and fill to a quarter of its depth with peanut oil. Heat the oil to 350 degrees F, or until a cube of bread turns golden brown in 15 seconds and floats to the surface. Ensure that your wok is stable before deep-frying.
Place the duck pieces in a spider/scoop, carefully lower into the oil and fry until crispy and golden brown. Remove from the pan and drain on paper towels.
To serve, spoon some crispy duck onto a tortilla and top with some Asian pear salsa. Serve with small bowls of cilantro, flaked sea salt and dried chile flakes so guests can season their own and help themselves.