In a large skillet over medium-high heat, add the toasted sesame oil.
Add the ground pork to the skillet, breaking it into small crumbles with a spatula, and cook until browned and fully cooked.
Stir in the minced garlic, grated ginger, diced red bell pepper, and chopped water chestnuts, sautéing for 3 minutes until the pepper is tender-crisp.
Season the pork mixture with sea salt and black pepper.
In a small bowl, whisk together the creamy peanut butter, tamari, lime juice, and sriracha until the sauce is smooth.
Pour the peanut sauce over the pork mixture and toss until everything is well-coated and fragrant.
Arrange the butter lettuce leaves on a plate and spoon the pork mixture into the center of each leaf.
Garnish with sliced green onions and serve immediately.