Use medium-low heat and resist the urge to stir frequently; let the mushrooms and onions sit undisturbed for 3-4 minutes between stirs to develop deep golden-brown caramelization.

Pat mushrooms completely dry with paper towels before cooking to prevent steam release, which allows proper browning instead of steaming.

Reserve a tablespoon of cold butter to stir in at the very end for a luxurious glossy coating and rich umami boost to your caramelized vegetables.

Add your all-purpose seasoning blend gradually throughout cooking rather than all at once, allowing flavors to build and preventing oversalting as liquids reduce.

Cut onions into consistent ¼-inch slices so they caramelize evenly at the same rate as your mushrooms for perfectly balanced texture and flavor throughout.