Pan-Seared Steak with Sauteed Mushrooms & Onions

My husband had waited long enough. It was due time for steak night. We used to eat steak once a week, but decided we both needed to eat a little healthier...so we cut back for a while. Needless to say, he was really excited last night!

This is a simple topping for a pan-seared steak, but it seems to take it to the next level. For an extra special treat, I cooked my hubby's fav steak - ribeye - and for me, a tenderloin.

Pan-Seared Steak with Sauteed Mushrooms & Onions
steaks of your choice (ribeye, tenderloin, sirloin, etc.)
3 tablespoons butter
salt & pepper
onion powder
garlic powder
2 tablespoons olive oil
5 oz. pack of mushrooms (baby portabellas are delicious, but any mushy will do)
1 medium yellow onion, chopped (you could also use shallots)
1/2 teaspoon balsamic vinegar
1/2 teaspoon Worcestershire sauce

Directions

1. Season steaks with salt, pepper, onion powder and garlic powder.
2. Put butter in nonstick pan and heat to medium-high. Add steaks to pan and once there's a nice sear, turn down the heat to medium (so you don't burn the bottom of the steak). Cook to your preferred doneness (roughly 3-4 minutes per side, depending on how thick the steak is), turn up the heat again and sear the other side. Then, bring the heat down and let the steak finish cooking.
3. Remove steaks and tent with foil.
4. At the same time, add 2 tablespoons olive oil to another nonstick pan or skillet, bring to medium heat. Add mushrooms and onions, and season lightly with salt and pepper. Saute for 2-3 minutes, until onions begin to get translucent. Add 2 tablespoons butter and continue sauteing for another 5 minutes. 
5. Add balsamic vinegar and Worcestershire sauce and stir. Season lightly with more salt. Taste, and add more of the vinegar or Worcestershire, if needed. Continue cooking until onions are translucent and mushrooms are soft.
6. Serve steaks with sauteed mushrooms and onions on top.