Step 1Combine the Shaoxing wine, oyster sauce, soy sauce, and ground white pepper in a small bowl or cup. Whisk until well mixed and set aside.
Step 2In a large skillet, heat the oil over medium-high heat until it begins to smoke lightly. Add the ground turkey, spreading it evenly across the skillet with a wooden spoon or spatula. Allow the meat to brown undisturbed for 4 to 5 minutes, ensuring the underside develops a rich, caramelized color. Break the turkey into smaller pieces and stir.
Step 3Incorporate the shiitake mushrooms and the white and light green portions of the scallions. Stir frequently, scraping the skillet’s bottom if necessary, until the mushrooms glisten and the scallions soften, approximately 2 minutes.
Step 4Pour in the reserved sauce mixture, followed by the diced celery and chopped cashews. Stir the mixture thoroughly, cooking just until the celery warms through and the turkey is fully cooked, roughly 1 minute. Remove the skillet from heat. Taste and adjust the seasoning with additional soy sauce or white pepper, as preferred.
Step 5Transfer the filling to a serving platter and garnish with the reserved scallion greens and celery leaves. To serve, spread a small amount of hoisin sauce onto a lettuce leaf, add a spoonful of the turkey mixture, and enjoy.