To make the sauce. In a jar, combine the Gochujang, Thai red curry paste, tamari/soy sauce, fish sauce (if using), ginger juice, toasted sesame oil, sesame seeds, and chili flakes. Add the oil and vegetables to a large skillet set over high heat. Cook for 3 minutes, until charring, then toss and cook another 2 minutes. Remove from the skillet to a plate.To the same skillet, add the onion and beef. Cook until the beef becomes crispy, about 5 minutes. Add half the sauce, tossing to combine. Cook until the sauce coats the beef. Add the vegetables and a few spoonfuls of sauce. Cook another 3-5 minutes. Mix in the pickled ginger. Remove from the heat. Serve the beef and vegetables over bowls of rice. Top with basil and sesame seeds. Serve with any remaining sauce.