Combine all of the marinade ingredients in a bowl and whisk well to combine. Add the chicken cubes and mix well.
Put the chicken cubes in a ziplock bag, seal and refrigerate for at least 4 or hours or (even better) overnight.
After the chicken has marinated, remove the bag from the refrigerator. Combine the panko and parmesan in a large bowl.
Toss the chicken cubes in the bread crumb mixture and thread the chicken on the skewers.
Grill the chicken, carefully turning once, until the chicken is cooked through, about 10 mins.
While the chicken cooks, whisk together the melted butter and lemon juice in a small bowl.
To serve, drizzle the lemon butter sauce over the chicken skewers or serve alongside.