Heat the toasted sesame oil in a large skillet over medium-high heat until shimmering.
Add the ground chicken mince to the pan, breaking it into small crumbles with a spatula until it is browned and fully cooked.
Stir in the minced garlic, grated fresh ginger, diced red bell pepper, and chopped water chestnuts, sautéing for 3 minutes until the vegetables are slightly softened.
In a small bowl, whisk together the coconut aminos, rice vinegar, and sriracha to create the glaze.
Pour the sauce over the chicken mixture and stir well to coat every piece, allowing it to simmer for 2 minutes until the sauce thickens.
Season the mixture with sea salt and black pepper, then fold in the sliced green onions and toasted cashew pieces for texture.
Wash and dry the butter lettuce leaves, arranging them on a platter for serving.
Spoon the warm chicken mince into the center of each lettuce leaf and serve immediately while the contrast of temperatures is at its peak.