Heat sesame oil in a large skillet over medium-high heat.
Add the ground beef and cook until browned, breaking it into small crumbles with a spatula.
Drain any excess fat from the skillet.
Stir in the diced onion, garlic, and ginger; sauté for 3 to 4 minutes until the onion is translucent.
Add the soy sauce, rice vinegar, sriracha, and water chestnuts to the skillet.
Simmer the mixture for 2 to 3 minutes until the liquid has slightly reduced.
Remove from heat and stir in the sliced green onions and shredded carrots.
Spoon the beef mixture into the center of each lettuce leaf and serve immediately.