Roughly chop the fresh parsley leaves and garlic cloves. Set aside.
Preheat the oven to 350°F/180°C.
Take a bowl or a plate. Combine butter, parsley and garlic.
Stuff butter mixture in-between the flesh and skin of the chicken. Turn to the other side of the chicken and stuff again.
Gently press with fingers on chicken skin to spread the butter mixture evenly.
Place onion, lemon halves inside the chicken.
Season the chicken with salt and pepper.
Tie the chicken legs using twine thread.
Place the chicken on baking tray, lined with aluminium foil.
Bake it for 60 to 75 minutes.
Serve hot with Mayonnaise.