In a bowl, mix together the soy sauce, hoisin sauce, rice vinegar, sesame oil, ginger, and garlic.
This will be your sauce base.
Set it aside for now.
Heat a skillet over medium-high heat and add the diced chicken breast.
Cook the chicken until browned and cooked through, approximately 5 to 7 minutes.
Add the chopped red bell pepper and water chestnuts to the skillet with the chicken.
Stir to combine and let them cook for about 3 minutes.
Pour the prepared sauce over the chicken and vegetables.
Stir well to coat everything evenly.
Let it simmer for another 2 minutes.
Turn off the heat and mix in the sliced green onions and chopped peanuts.
Serve the mixture in butter lettuce leaves.