Combine water, salt, whole chicken, chicken bones, 1 sliced onion, ginger, cinnamon, star anise and cardamom pods in a large pot and bring to the boil. Skim off any froth that rises to the surface, lower heat and simmer for 1½ hours. Remove whole chicken and reserve.
Add sugar, 2 tablespoons deep-fried shallots and fish sauce to stock and cook for another hour. Strain stock through a fi