Peking Duck Breasts

Name: Peking Duck Breasts
Ingredients: 2 tablespoons hoisin sauce, plus more for serving; 1 tablespoon oyster sauce; 2 cloves garlic, grated; 1 tablespoon grated ginger; 1 scallion, minced; 1 teaspoon sugar; 1/2 teaspoon Chinese five-spice powder; 1/4 teaspoon ground white pepper; Kosher salt; 2 duck breast halves (about 1 1/2 pounds); 3 scallions, cut into 2-inch julienne (matchstick-size pieces); 1 English cucumber, seeds removed, julienned (cut into matchstick-size pieces); Frozen Peking duck wrappers or steamed bao buns