Heat oil in a medium saucepan. Add garlic and ginger and saute for a few seconds to release the aroma. Add the broth and water and bring to a boil. Add the rice and boil for 10 minutes or until tender. Add the frozen chicken and simmer just until cooked through. Add the peas and simmer just to heat through. Season to taste with salt, pepper and lemon juice. Remove the soup from the heat and add parsley and scallions.