1. Prepare the Chicken: Start by cutting your boneless, skinless chicken thighs or breasts into uniform 1-inch cubes. Aim for pieces that are roughly the same size so they cook evenly on the grill.

2. Whisk the Marinade: In a medium bowl, combine the soy sauce, brown sugar, sesame oil, rice vinegar, grated fresh ginger, minced garlic, gochujang (if using), and black pepper. Whisk everything together until the brown sugar is fully dissolved and the marinade is well combined.

3. Marinate the Chicken: Add the cubed chicken to the bowl with the marinade, tossing to ensure all the chicken pieces are thoroughly coated. Cover the bowl and refrigerate for at least 30 minutes, or up to 2 hours. If you’re using wooden skewers, this is a good time to soak them in water to prevent them from burning on the grill.

4. Thicken the Sauce (Optional but Recommended): While the chicken marinates, pour about half of the marinade into a small saucepan. In a separate small bowl, whisk together the cornstarch with 2 tablespoons of water to create a slurry. Add the cornstarch slurry to the saucepan with the reserved marinade. Bring to a simmer over medium heat, stirring constantly, until the sauce thickens slightly, about 2-3 minutes. This will be your delicious Asian BBQ dipping or basting sauce.

5. Assemble the Skewers: Thread the marinated chicken pieces onto your prepared skewers. Don’t pack them too tightly; leave a little space between each piece for even cooking. Discard any remaining marinade that touched the raw chicken.

6. Preheat and Grill: Preheat your grill to medium-high heat (about 400 F / 200 C). Lightly oil the grill grates to prevent sticking. Place the chicken skewers on the hot grill.

7. Cook to Perfection: Grill the skewers for 10-15 minutes, turning them every 3-4 minutes, until the chicken is cooked through and has nice char marks. The internal temperature of the chicken should reach 165 F (74 C). If desired, you can baste the skewers with some of the thickened sauce during the last few minutes of grilling for extra flavor and glaze.

8. Serve Hot: Remove the cooked skewers from the grill and let them rest for a few minutes before serving. Serve with the reserved thickened Asian BBQ sauce for dipping.