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Chill the soup in the refrigerator overnight.
Once you’ve finished cooking the soup, remove it from the heat and cover the stockpot with cling wrap or aluminum foil. Allow it to cool down at room temperature for about 10 to 20 minutes, then place it in the refrigerator. Leave it to chill for at least 6 to 8 hours, or until the fat floats to the top and completely hardens.  Try to prepare your soup the night before so it has time to chill overnight. If you need to serve the soup right away, this technique won't be suitable. Try skimming the fat while you’re cooking the soup or straining the broth instead.