In a bowl, mix together hoisin sauce, soy sauce, rice wine vinegar, garlic chili sauce, ginger, and sugar. Set aside.
Chop onions, garlic, and water chestnuts.
Heat a large sauce pan over medium heat.
Add onions and cook until soft, about 3-4 minutes.
Add garlic and tofu. Cook 5-6 minutes. While cooking, crumble the tofu until it resembles fine crumbles.
Stir in chopped water chestnuts and cook for 2 minutes, stirring occasionally.
Add in green onions and sauce mixture. Cook another 1-2 minutes. Season with salt and pepper, to taste if desired.
To serve, spoon several tablespoons of the mixture into the center of a lettuce leaf. Serve with rice.