Chef Ludo Lefebvre's French Onion Soup Recipe Is Definitely Worth Memorizing

"It's like eating a liquid sandwich. It's so good!" It's no surprise that French onion soup is one of the most ordered menu items at Petit Trois, Ludo Lefebvre's Los Angeles bistro. As the chef puts it, "It can be cold outside — yes! — you sell onion soup. When it's hot outside, do you want to eat …