Prep the veggies and sauce. Dice the onion, pepper, mushrooms, and water chestnuts.
Mince the garlic and ginger. In a small bowl, whisk soy, oyster, hoisin, rice vinegar, honey, chili-garlic sauce, sesame oil, water, and cornstarch until smooth.
Heat the pan properly. Set a large skillet over medium-high heat. Add the oil and let it shimmer.
A hot pan ensures the pork browns instead of steams.
Brown the pork. Add the ground pork and break it into small crumbles. Let it sit for 1–2 minutes before stirring so it caramelizes. Cook until no longer pink and lightly browned, about 5–6 minutes.
Drain excess fat if needed.
Build the flavor base. Add onion, mushrooms, and bell pepper. Cook 3–4 minutes until softened. Stir in garlic and ginger and cook 30–45 seconds until fragrant.
Simmer with sauce. Pour in the sauce.
Stir to coat and let it bubble for 1–2 minutes until slightly thickened and glossy. Fold in water chestnuts and half the green onions. Taste and adjust salt, sweetness, or heat.
Prep the lettuce. Separate and rinse the leaves.
Pat dry well—dry leaves hold the filling better.
Assemble and garnish. Spoon the pork mixture into lettuce cups. Top with remaining green onions, cilantro or mint, sesame seeds, and a squeeze of lime.
Serve immediately. Offer rice or noodles on the side if you want a more filling meal.