Onions should be clear and very tender once finished. Cover the stock pot and cook for around 20 minutes checking to make sure they aren’t burning. Stir the sliced onions into the oil/butter mix, ensuring they are evenly coated. Heat a heavy, oven-safe, stock pot over medium-low heat and add the cooking oil once the pot is hot. So get out your apron, and prepare to indulge in a classic French favorite. This recipe by Julia Child takes a little longer than many simpler recipes, but it’s well worth the time spent. French Onion Soup has to be on the top of my list for favorite soups.