Follow these straightforward steps to create your Honey Dijon Chicken Sandwiches:

1. Prepare the Marinade: In a bowl, combine the Dijon mustard, honey, olive oil, garlic powder, salt, and pepper. Mix until well blended.
2. Marinate the Chicken: Place the chicken breasts in a shallow dish or zip-top bag. Pour the honey Dijon mixture over the chicken, ensuring each piece is evenly coated. Marinate for at least 15 minutes.
3. Preheat the Grill: Heat your grill or grill pan over medium-high heat. Lightly oil the grill grates to prevent sticking.
4. Grill the Chicken: Once hot, place the marinated chicken on the grill. Cook for about 6-7 minutes on each side, or until the internal temperature reaches 165°F (75°C).
5. Toast the Buns: As the chicken is cooking, lightly toast your sandwich rolls or brioche buns on the grill until golden.
6. Assemble the Sandwiches: Once the chicken is cooked, slice it into strips. Layer the arugula or spinach on the bottom half of each bun, add the chicken, followed by sliced tomatoes and cucumbers. If desired, top with cheese.
7. Serve and Enjoy: Place the top half of the bun on each sandwich, secure with a toothpick if needed, and serve immediately while warm.

These steps will guide you in easily creating delicious Honey Dijon Chicken Sandwiches that you can enjoy any day of the week.