• Remove the gizzards and any internal organs inside the chicken's cavity. Under cold running water, rinse chicken well. Thoroughly dry the chicken inside and out.
• In a food processor, pulse garlic until smooth. In a small bowl, combine pureed garlic and pepper.
• Generously rub the chicken inside and out with rock salt. Massage the chicken inside and out with the garlic and pepper mixture. Let stand for about 20 to 30 minutes. 
• Remove and discard the dark green layers of the lemongrass until you get to the lighter green part. With a knife, cut into lengths that will fit inside the chicken's cavity. Using the back of the knife, pound ends of lemongrass to release flavor.
• Peel the onion and cut one end to level.
• Stuff lemongrass into the chicken cavity. Insert onion with cut side facing outwards.
• In a large, thick-bottomed pot, add rock salt to about 1 ½ to 2 inches deep. Line banana leaves on top of the salt. 
• Position chicken on an upright, "sitting" position on banana leaves. 
• Cover pot with a tight-fitting lid. Over medium heat, cook chicken for about 1 ½ to 2 hours or until a thermometer inserted in the thickest part reads 165 F.
•  Gently lift chicken from pot and arrange on a serving platter. Serve hot with dipping sauce.

Dipping Sauce

• In a bowl, combine lemon juice and fish sauce or soy sauce to taste.