1) Rinse the lettuce leaves, taking care not to tear them as you separate them. Pat dry and set aside.
2) In a large skillet over medium-high heat, brown the ground beef in 1 tablespoon of the olive oil, breaking up with the back of a wooden spoon. Drain and set aside.
3) In the same pan add the remaining 1 tablespoon of olive oil. Add the onions and saute, stirring frequently. Cook until translucent.
4) Add the garlic, coconut aminos, hoisin sauce, and vinegar to the onions. Stir to combine and cook for 1 minute.
5) Add the water chestnuts, green onions, sesame oil, and browned beef. Stir to combine and cook just until the green onions begin to wilt, about 2 minutes.
6) Remove from heat and transfer to a serving bowl.
7) To serve, spoon beef mixture into the well of the lettuce leaves, fold up like a taco and eat. Yum!