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Steak Mushroom Onion Skillet: a porterhouse steak in a cast-iron skillet with caramelized mushrooms and onions. The skillet sits atop a colorful striped cloth.

Steak Mushroom Onion Skillet

Steak Mushroom Onion Skillet makes a perfect special occasion dinner, whether it's Date Night or a holiday dinner for two.
Course Entree
Cuisine American/Comfort Food
Keyword keto, paleo, skillet dinner, skillet steak, steak with mushrooms and onions, whole 30
Prep Time 30 minutes
Cook Time 20 minutes
resting 10 minutes
Total Time 1 hour
Servings 2


  • 1 porterhouse or ribeye steak about 2" thick, 2 lbs.
  • 1 tbsp butter unsalted
  • 1 tbsp olive oil extra virgin
  • 8 oz cremini mushrooms trimmed and sliced
  • 2 cups vidalia onion sliced into half-rings (see Recipe Note #1)
  • 6 dashes Maggi seasoning sauce (see Recipe Note #2)
  • 3/4 tsp kosher salt divided (or to taste)
  • 3/4 tsp freshly ground black pepper divided (or to taste)


  • Pat the steak dry thoroughly with paper toweling. Salt and pepper liberally. Cover with plastic wrap and rest at room temperature for 30 minutes.
  • When the steak is 5 minutes away from the end of its rest, set a cast-iron skillet over medium heat. After 2 minutes, add the butter and olive oil. When the butter is melted, tilt the pan to spread the butter and olive oil all around the skillet. Add the steak. Leave undisturbed until the bottom of the steak is nicely caramelized, about 5 minutes. 
  • Flip the steak and cook until it reaches your desired level of doneness (see Recipe Notes #3 and #4). While the steak cooks, baste it frequently by spooning the butter/olive oil mixture in the skillet over the top of the steak. 
  • Remove the steak to a cutting board and rest for at least 5 minutes and up to 10.
  • Meanwhile, cook the mushrooms and onions. Without wiping out the pan, add the mushrooms and onions. Saute over medium heat until the mushrooms have given up their liquid and the onions are softened, about 5 minutes. Add the Maggi seasoning (or coconut aminos), 1/4 tsp salt, and 1/2 tsp black pepper. Continue sauteing until the vegetables develop a bit of caramelization, about 5 additional minutes.
  • Slice the steak against its grain and serve with the mushrooms and onions.


  1. If you are following a diabetic or low-carb diet, please note that the vidalia onion does contain some carbs, so keep that in mind and adjust how much you eat if you're near your daily carb limit. 
  2. If you are following a paleo, whole 30, or gluten-free diet, you can substitute coconut aminos for the Maggi seasoning sauce.
  3. To get a general idea of "where the steak is" in the cooking process, I press the center of the meat with my index finger. I compare the "give" of the meat to what it feels like if I press on different parts of my face (a.k.a., the "face test"):
    • The hollow of my cheek (fleshy with no resistance) = approximately rare
    • My chin (fleshy with some resistance) = approximately medium
    • My forehead (firm with more resistance) = approximately well done.
  4. For best results, check the final temperature with an instant read thermometer inserted into the thickest part of the meat (don't touch bone!). Doneness guidelines:
    • Rare (120º F – 130º F)
    • Medium Rare (130º F – 140º F)
    • Medium (140º F – 150º F)
    • Medium Well (150º F – 160º F)