Pour the onion soup mixture evenly over the onions and patties in the slow cooker, making sure everything gets a little bit of that concentrated flavor.
Cover the slow cooker with the lid and cook on LOW for 5 to 7 hours, or on HIGH for 2 1/2 to 3 1/2 hours, until the burger steaks are cooked through (no pink in the center) and very tender. The onions should be soft and the liquid will have turned into a savory, spoonable gravy.
Cooked burger steaks in onion gravy inside slow cooker
Cooked burger steaks in onion gravy inside slow cooker
Once cooked, carefully lift the burger steaks out with a wide spatula, keeping as many onions on top as you can, and transfer them to plates or a serving platter. Stir the remaining onions and gravy in the slow cooker, then spoon the mixture generously over the top of the burger steaks.
Taste the gravy and add a pinch of extra salt or pepper if needed, then serve the French onion burger steaks hot over mashed potatoes, noodles, or rice, making sure to use every last bit of those slow-cooked onions.
Variations & Tips
For a cheesier French onion twist, top each burger steak with a slice of provolone, Swiss, or mozzarella right after cooking and cover the slow cooker for 5 to 10 minutes until the cheese melts.
If you prefer a thicker gravy, whisk 1 tablespoon cornstarch with 2 tablespoons cold water, stir it into the hot onion gravy in the slow cooker, and cook on HIGH for 10 to 15 minutes until slightly thickened. You can swap the condensed French onion soup for condensed beefy mushroom soup if that’s what you have on hand; the onion flavor will still come through from the dry onion soup mix and sliced onions.
Cheesy French onion burger steak variation with melted provolone
Cheesy French onion burger steak variation with melted provolone
For a bit of extra depth, add 1 teaspoon Worcestershire sauce or a splash of soy sauce to the soup mixture before pouring it over the patties (this would technically add another ingredient, but it’s an easy upgrade). Use lean ground turkey instead of beef for a lighter version—just be sure not to overcook, as turkey can dry out more quickly.
If you’re prepping ahead, you can shape the patties and slice the onions the night before, then in the morning simply layer the raw patties and onions in the slow cooker, pour on the soup mixture, and turn it on before heading out the door.
