In a large skillet, heat the vegetable oil over medium heat. Add the chopped onion and sauté until translucent, about 3-4 minutes.
Add the minced garlic and cook for an additional 1 minute until fragrant.
Stir in the ground beef or turkey, breaking it apart with a spatula. Cook until browned and cooked through, about 5-7 minutes.
In a small bowl, whisk together the soy sauce, brown sugar, gochujang, sesame oil, ginger, and black pepper. Pour this mixture over the cooked meat and stir to combine. Cook for another 2-3 minutes until heated through.
While the meat is cooking, prepare the Yum Yum Sauce by whisking together mayonnaise, ketchup, rice vinegar, sugar, garlic powder, paprika, salt, and pepper in a separate bowl. Adjust seasoning to taste.
Warm the tortillas in a dry skillet or microwave until pliable.
To assemble the tacos, place a generous spoonful of the meat mixture on each tortilla. Top with shredded cabbage, carrots, green onions, and cilantro. Drizzle with Yum Yum Sauce.
Serve immediately and enjoy!