Rinse chicken and place in a large, deep saucepan. Add cold water and slowly bring to a boil over medium heat. Add onion, 2 stalks of celery, 2 carrots and peppercorns. Reduce heat and simmer, using a spoon or ladle to skim foam that rises to the surface. Stir in 1 tsp (5 mL) salt. Simmer stock, uncovered, for 2 hours, occasionally skimming fat and foam that collect on top.