Try this French Onion Soup recipe
Maillard browning requires temperatures above 300 degrees Fahrenheit to break down amino acids and reducing sugars into complex flavor compounds. Sautéing the sliced yellow onions in butter for twenty total minutes initiates this caramelization before sealing the cooker. Adding sugar accelerates the Maillard reaction by supplying extra monosaccharides for the heat to act upon. Stir constantly during the final seven minutes of the sauté phase to prevent scorching the bottom of the pot.
Assessing the onions relies entirely on visual and olfactory cues rather than a thermometer. They are fully browned when the volume reduces significantly and the strands turn a deep amber color. Deglazing with dry white wine or sherry dissolves the fond stuck to the metal surface. Simmer this liquid until fully evaporated to eliminate harsh alcohol notes while retaining acidic depth.
Pressure cooking at high pressure for five minutes breaks down remaining structural cell walls in the onions. Quick-releasing the pressure halts the cooking process immediately to preserve texture. Beef broth provides the primary liquid base, absorbing the dissolved onion aromatics during the pressure cycle. Ladle the finished broth into ovenproof bowls placed securely on a large baking sheet for stability under the heat source.
Broiling the assembled bowls for one to two minutes melts the shredded Gruyère or Swiss cheese over the toasted French bread slices. Watch the broiler closely because high radiant heat burns dairy fats quickly once the moisture evaporates. Scaling the ingredient quantities up or down requires maintaining the ratio of four medium onions to eight cups of broth to keep the flavor concentrated.