To prepare the glaze, bring the rice vinegar, chili flakes, garlic and onion to a medium simmer in a heavy sauce pot and reduce by half. Add the brown sugar, tomato paste, soy sauce, salt and bring it back to a full simmer for about 5 minutes. Remove from heat and whisk in the butter. Cover and keep warm to serve with the duck.
De-breast the wild duck and season the breasts with salt and pepper. Prepare your grill and place the duck breasts, skin side down, on the grill. Grill until the skin is crispy but not black. Turn the breasts over and grill for another 2 minutes or until the interior meat is light pink. Do not overcook! Remove from heat and cover with foil to keep warm until ready to serve.
When ready to plate, slice the duck breast thinly and serve over a bed of rice. Ladle a spoonful of the warm glaze over the top of the duck breast and serve immediately. Serves 6-8.