Flank Steak, Caramelized Onion, Mushroom and Blue Cheese Panini

I was in the mood for a panini sandwich for dinner. I decided to marinate some flank steak in a balsamic, Dijon and garlic marinade. Looking through my refrigerator and pantry I found an onion, mushrooms, mayonnaise, garlic and low fat blue cheese (it’s really good and has great flavor) – all the ingredients you need for a tasty steak sandwich. I always make my panini sandwiches “dry” instead of coating them with oil and they turn out extra crispy without being greasy. This was an excellent sandwich that we all enjoyed. My son and I had blue cheese. My husband, who doesn’t care for blue cheese, had Swiss and my daughter had no cheese. These sandwiches were easy to make with little clean up.

Flank Steak Marinade:
Recipe and photos by For the Love of Cooking
  • Flank steak
  • 1/2 cup balsamic vinegar
  • 1/4 cup olive oil
  • 1 tbsp Dijon mustard
  • 1 tsp brown sugar
  • 3 cloves of garlic, minced
  • Sea salt and freshly cracked pepper to taste

Combine all ingredients in a large zip lock bag and mix thoroughly. Add the flank steak and marinate in the refrigerator for 2-8 hours.

Roasted Garlic Mayonnaise:

  • 1 bulb of roasted garlic
  • Light Mayonnaise
  • Sea salt and freshly cracked pepper

Make the roasted garlic (see link). Combine the mayonnaise, cooled roasted garlic (squeezed from the skin), sea salt and fresh cracked pepper, to taste. Mix thoroughly. Refrigerate until needed.


  • 1 tbsp olive oil (divided)
  • 1 sweet yellow onion, sliced thick
  • 15 button mushrooms
  • 1 clove of garlic
  • Thin slices of good bread
  • Marinated flank steak

Heat half of the olive oil in a large skillet over medium heat then add the onion slices. Cook, stirring occasionally, for 20-30 minutes or until golden brown. Season with sea salt to taste then remove from heat and set aside.

Grill the steak to your desired degree of doneness. Make sure to let the meat “rest” for at least 5 minutes prior to slicing. Slice steak against the grain into thin slices.

While the steak is grilling, heat the remaining oil in the large skillet over medium high heat. Add the mushrooms and leave them alone without stirring for 3-5 minutes. Stir them with a spatula and cook for an additional 3-4 minutes or until golden brown. Add the minced garlic and season with sea salt to taste, cook for an additional 60 seconds while stirring constantly. Remove from heat and set aside.

Preheat the panini maker. Slather the roasted garlic mayonnaise on each slice of bread, layer one slice of bread with thinly sliced flank steak, caramelized onion and mushrooms, cheese and remaining slice of bread. Place dry sandwich on the panini maker and cook for 5 minutes. Slice in half and serve. Enjoy.

(With Swiss cheese)

Click here for a printable version of this recipe – For the Love of Cooking.net

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4 Responses to “Flank Steak, Caramelized Onion, Mushroom and Blue Cheese Panini”

  1. 1

    Krista — May 23, 2012 @ 4:46 pm

    Making this for dinner tonight. Can’t wait! How much mayo do you use per bulb of garlic? Thanks!


    • Pam replied: — May 23rd, 2012 @ 5:23 pm


      I just used enough mayonnaise for my taste. I would start with a tablespoon then taste and add more if you desire. I hope you love this sandwich as much as I did!



    • Krista replied: — May 23rd, 2012 @ 7:36 pm

      Oh. my. word. SO delicious! Thank you!!


  2. 2

    lisa — August 6, 2012 @ 10:21 am

    I marinaded thick slices of steak with little sweet chilli sauce,soya sauce,whole grain mustard,honey,mixed dry herbs,olive oil …..only gorgeous,if ya can get your hands on some A1 sauce even better with the mayo…..


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