Porterhouse for 2 with Onion Mustard sauce

What sets a ho-hum steak apart from an "Out of this World" steak?  Seasoning!  And of course, not over cooking it.  Porterhouse is one of our faves because it's perfect for 2.  My husband eats the larger strip side and I eat the smaller filet side.  A Porterhouse steak is a beautiful YET pricey piece of meat so you don't want to ruin it by not properly cooking it.  I have found the meat thermometer from OXO to be the best and the most user friendly.  It has just enough bells and whistles to be useful but not too many to be confusing.  I also love it's long compact shape because it fits perfectly at the front of any kitchen drawer and the long cord wraps around the device and the probe tucks neatly inside. 

Being on a keto/low carb diet not only allows but encourages us to eat real meat and real fat.  Yes, real animal fat!

Here are internal temperatures for your convenience

Rare 140 degrees
Medium Rare 145 degrees
Medium 160 degrees
Well Done 170 degrees

Yield: 2 Servings 

Porterhouse for 2 with Onion Mustard Sauce

Porterhouse Steak topped with a Caramelized Onion & Mustard Sauce


  • 1 TBLS. Ghee
  • 18 oz Porterhouse Steak
  • 1 small White Onion, thinly sliced
  • 1/2 TBLS. Stone Ground Mustard or Dijon Mustard
  • 1/2 c. Beef Broth or Stock
  • Salt and Freshly Ground Pepper to taste


  1. Salt steak liberally.  Place on a  plate and let come up to room temperature.  Should take around 30 minutes.  
  2. In a cast iron or stainless steel skillet, melt the ghee over medium-high heat.  Add the steak and cook on both sides until the desired doneness is reached.   If you are not comfortable estimating doneness then use a meat thermometer.  Do not move the steak around while it's cooking or poke it with anything sharp. You want to get a good sear on both sides.  And moving it around will disturb that process. 
  3. Once the steak is finished cooking remove it from the skillet and season with pepper.  Place on a plate and tent lightly with foil.   I do not pepper my steak before cooking it.  Pepper can burn easily and when it does it leaves a very bitter burned taste on the steak.
  4. While the steak is resting, add sliced onions to the skillet and saute for a few minutes.  Stir in the mustard until the onions are coated with it.  Pour in the beef broth to deglaze the bottom of the skillet.  With a metal spatula, begin scraping up the bottom of the yummy brown bits from the pan.  Add any juices from the plate that have released from the steak while it was resting. 
  5. Lower the heat to medium and simmer while stirring the sauce.  Keep stirring until the sauce thickens and the onions are cooked until tender.  This will take about 5 minutes.  
  6. Spoon the Onion Mustard sauce over the steak and serve. 


*I use ghee instead of butter because it has a higher smoke point.  Since the milk solids have been removed from the ghee it is casein and lactose-free.
*I have used a lot of different mustards when making this onion mustard sauce.  And an old world style whole mustard seed mustard is the very best.  Although a regular Dijon mustard is also pretty darn good.
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