In a small bowl, combine teriyaki sauce, Dijon mustard, minced garlic, and sesame seeds. Stir until well-blended.

Place the chopped chicken breast in a resealable bag. Pour the marinade over the chicken, seal the bag tightly, and massage gently. Let it marinate in the refrigerator for at least 2 hours, up to 24 hours.

If using wooden skewers, soak them in water for about 30 minutes.

Fire up your grill and set it to medium-high heat.

Assemble your skewers by alternating marinated chicken, fresh pineapple, red bell pepper, mushrooms, and onion.

Grill the skewers for 10-14 minutes, flipping every 3 minutes until chicken reaches 165°F (75°C).

Let the kabobs rest for about 5 minutes before serving. Garnish with sliced green onions.