Step 1: Prepare the Chicken. Pat the boneless, skinless chicken breasts dry with paper towels. Cut them into approximately 1-inch cubes. Place the chicken cubes in a large bowl.
Step 2: Marinate the Chicken. To the bowl with the chicken, add the olive oil, minced garlic, fresh lemon juice, lemon zest, chopped fresh parsley, chopped fresh oregano, salt, and black pepper. Toss everything together until the chicken is thoroughly coated. Cover and refrigerate for at least 30 minutes, or up to 4 hours.
Step 3: Prepare the Breadcrumb Coating. In a shallow dish or plate, combine the panko breadcrumbs and grated Parmesan cheese. Mix well. (Optional: lightly toast panko in a dry skillet for 2-3 minutes before mixing with Parmesan for extra crunch).
Step 4: Thread the Skewers. One by one, dredge each marinated chicken cube in the breadcrumb mixture, pressing gently to ensure a good coating. Thread the coated chicken pieces onto skewers, leaving a little space between each piece. If using wooden skewers, soak them in water for 30 minutes beforehand.
Step 5: Preheat and Prepare for Cooking. Preheat your grill to medium-high heat (about 400°F/200°C) or your oven to 425°F (220°C). If grilling, lightly oil the grates. If baking, line a baking sheet with parchment paper or foil and place a wire rack on top.
Step 6: Cook the Spiedini. If grilling, place skewers on the preheated grill and cook for 3-4 minutes per side, turning occasionally, until chicken is cooked through and breading is golden brown and crispy. If baking, arrange skewers on the wire rack and bake for 18-25 minutes, flipping halfway, until chicken is cooked through (165°F/74°C internal temperature) and breading is crisp. (Optional: broil for 1-2 minutes for extra crispness).
Step 7: Serve Immediately. Remove the chicken spiedini from the grill or oven. Let them rest for a few minutes before serving. Garnish with extra fresh parsley and a wedge of lemon. Enjoy!