To begin, in a large bowl, combine the soy sauce, sake, mirin, sugar, garlic, sesame oil, and grated ginger. Stir until the sugar dissolves completely. This marinade will infuse the meat with a deep, savoury flavour.

Add the thinly sliced beef to the marinade, ensuring each piece is well coated. Cover the bowl and refrigerate for at least 30 minutes, or up to 2 hours, to allow the flavors to fully penetrate the meat.

While the meat marinates, prepare the vegetables. Slice the onion, bell pepper, mushrooms, and zucchini into bite-sized pieces. Arrange them on a platter for easy grilling.

Prepare the grilling sauce by mixing soy sauce, mirin, sugar, sesame oil, and gochujang (or miso) in a small bowl. Stir until the ingredients are well combined. Set the sauce aside for serving later.

Heat your grill or a grill pan over medium-high heat. If using an electric or table top grill, preheat to around 200°C (390°F). For a more traditional experience, a charcoal grill can be used, which adds a smoky depth to the flavour.

Begin grilling the marinated beef slices. Cook each side for 1-2 minutes until the meat is nicely caramelized and cooked through. Be careful not to overcook the thin slices, as they cook quickly. For best results, grill in small batches to ensure even cooking.

Grill the vegetables alongside the meat. The onions should be soft and slightly charred, while the peppers, mushrooms, and zucchini should be tender yet retain some bite. Use a light oil spray if the vegetables begin to stick to the grill.

Serve the grilled beef and vegetables with the dipping sauce on the side. Garnish the meat with toasted sesame seeds for added texture and flavour. Pair the dish with steamed rice, pickled vegetables, or kimchi for a full, balanced meal. Encourage diners to dip each bite of grilled meat into the sauce for maximum flavour.