In a small bowl, whisk together the tamari, sriracha, toasted sesame oil, honey, minced ginger, and garlic to create the savory glaze.
Season the diced chicken breast evenly with the sea salt and black pepper.
Heat a large non-stick skillet over medium-high heat and add the chicken, sautéing until golden brown and fully cooked through for about 6 minutes.
Add the diced red bell pepper and water chestnuts to the skillet, cooking for another 2 minutes until the vegetables are slightly softened but maintain their crunch.
Pour the sriracha glaze over the chicken mixture and toss well to coat, simmering for 1 minute until the sauce thickens and becomes glossy.
Remove the skillet from the heat and stir in the sliced green onions.
Wash and pat dry the butter lettuce leaves, then spoon the chicken mixture evenly into the center of each leaf.
Garnish with crushed cashews for added texture and serve immediately while warm.