In a large mixing bowl, combine gochujang, brown sugar, soy sauce, water, sesame oil, rice wine vinegar, minced garlic, minced ginger, kosher salt, and black pepper. Stir until well blended. Place the chicken wings in a resealable bag, pour the marinade over them, and seal the bag, ensuring the wings are thoroughly coated. Refrigerate and allow to marinate for at least 1 hour, or overnight for maximum flavor.

When you're ready to cook your wings, preheat your grill to medium-high heat or your oven to 400°F (200°C). Clean and lightly oil the grill grates if using a grill.

Grill the marinated wings for approximately 30–40 minutes, flipping every 10–15 minutes until crispy and golden, reaching an internal temperature of 165°F (74°C). If baking, arrange wings in a single layer on a parchment-lined baking sheet and bake for 40–60 minutes, turning halfway through.

While the wings are cooking, pour the reserved marinade into a saucepan. Bring to a boil over medium heat and simmer for 1–2 minutes to thicken.

Once the wings are cooked, brush them generously with the boiled sauce and sprinkle sesame seeds and sliced green onion over them before serving.