01 - Heat vegetable oil in a large skillet or wok over medium-high heat. Add ground beef and cook, breaking up with a spatula, until browned and just cooked through, about 4 to 5 minutes.
02 - Add garlic, onion, carrot, and red bell pepper to the skillet. Stir-fry for 2 to 3 minutes until vegetables are tender-crisp.
03 - Add cashew nuts and spring onions to the mixture, stirring to combine evenly.
04 - In a small bowl, whisk together soy sauce, hoisin sauce, oyster sauce, sesame oil, ginger, brown sugar, and chili flakes until well combined.
05 - Pour sauce over beef mixture and stir well to coat. Cook for another 1 to 2 minutes until heated through and fragrant.
06 - Remove from heat and taste for seasoning adjustments. Spoon beef-cashew mixture into lettuce leaves, garnish with cilantro, and serve with lime wedges.