Chicken and lemon grass with potato soup

Ingredients

• 3 chicken tight or 1/2 chicken, removed skin
• 4 - 5 potato, peeled and cut to four pieces each
• 1 whole red onion, peeled and cut into 4 pieces
• 5 - 6 lemon grass, trim and smashed
• 1 small pig stomach, clean and rub with salt
• 5 cup water
• 1 can chicken broth
• 1 teaspoon salt
• 1/2 teaspoon sugar
• 1 tablespoon peppercorn seed, smashed
• 1/3 cup distilled vinegar