Caramelized Onions & Mushroom Panini... to heaven and back!

Happy St. Patrick's Day!

My best-est friend, Jhiane, came over today to chill with me after so long, unfortunately her stay wasn't long enough though.  She's a busy lady and always double books when she hangs with me, it's annoying, but I forgive her.  :-)  

And then we did a bad thing which is so typical of us.  We ended up grabbing an early dinner at Soul Flavors which was greasy and comforting American food, I KNOW!  My diet plan is going out the window this week, but I'll have to workout extra hard tomorrow.  No sweat = No gain!

So this past week I had some mushrooms at home and decided to make Mushroom Paninis for my husband and I.  I took this recipe up several notches by caramelizing the onions with butter in a Cast Iron Skillet - oh yeah!  Sound good, right?  It was delectable!  

I took this recipe up yet another notch by adding thyme, an earthy, woody spice, that I often see celebrity chefs Tyler Florence and Ina Garten adding to mushrooms.  Adding thyme gave these paninis an earthy flavor that I loved.  Lastly, I used a tablespoon of butter (not so terrible) to caramelize the onions because there is something about sauteing butter and onions in a Cast Iron Skillet, however feel free to use Olive Oil if fat is an issue.  Keep in mind if you use butter, one sandwich will easily fill you up.  Either way, I'm positive you guys will love this.

Note to my Brother, who thinks he's the "soup and sandwich chef" in the family: Take that Bits!  Montreal Chicken Seasoning is NOT the answer to every dish.  :-)

NUTRITION: Mushrooms are a very good source of Vitamin B6 and Protein.  Cheese is a good source of Calcium and Protein.  Whole Wheat Bread adds Fiber and Protein to this dish.


For the Caramelized Onions & Mushrooms (makes 4 sandwiches):
  • Butter - 1 tbsp (you can use 1 tbsp Olive Oil instead)
  • Onion - 1 medium (sliced)
  • Baby Bella (Crimini) Mushrooms - 1 8 ounce box (sliced)
  • Black Pepper - 1/2 tsp
  • Crushed Red Pepper Flakes - 1/2 tsp (use less if you can't handle heat)
  • Thyme - 1/2 tsp
  • Garlic Powder - 1 tsp
  • salt to taste
For the Sandwich: 
  • Butter - very little or enough to grease the skillet
  • 100% Whole Wheat Bread - 2 slices at a time
  • Mozzarella Cheese - enough to cover a slice of bread

1. Start by slicing a medium onion.

2. Heat a Cast Iron Skillet on medium to high heat, wait until it's hot, add butter.

3. Once melted, add the onions.  Season with salt and saute for 10 minutes or until slightly caramelized.

4. In the meantime, slice your mushrooms.

5. Back to the onions, this is what you should have.

6. Add the mushrooms, salt, and black pepper.  Saute for 5 minutes or until the mushrooms brown and release a little liquid.

7. In the meantime, get your spices out.

8. Once the mushrooms brown, add the garlic powder, thyme, and crushed red pepper flakes.  

9. Combine and cook for another few minutes.  There should be no liquid in the skillet. Transfer the mushrooms to another bowl.

10. In the same Cast Iron Skillet, lower the heat to dial #3.  Grease the skillet with butter - very little.  

11. Place 2 slices of bread.  Allow them to toast up for 30-60 seconds.  

12. Flip both slices of bread. 

13. Now add the mushrooms.

14. Top with mozzarella cheese.  You can use Mexican Cheese or whatever else you like.

15. Top with the other slice of bread.

16. Place a heavy lid (or skillet) over the bread and push down a little.  This will help the cheese melt to perfection.

17. Flip.  

18. Again, use a heavy lid and push down a little. 

19. Slice in half.  Repeat process for the next sandwich.  

TELL ME: Have you used 'Thyme' before?  If so, what do you use it in?


  1. This looks great! I don't have a cast iron skillet though. Is it possible to caramelize the onions with a regular skillet?

  2. @Mari - Sure, you can use a regular skillet, however cooking in a Cast Iron Skillet will result in a much better flavor, perhaps more caramelization. In terms of health a cast iron skillet is a much better option than cooking in a nonstick skillet. But sure, you can use a regular skillet. :-)

  3. This panini looks great! I love caramelized onion and mushrooms! Mmmm... :)

  4. I definitely have to try this it looks so yummy.

  5. Oh yum yum yum!!! The oozing cheese is just too much, I need to get a bite ;)!!

  6. This looks amazingly delish. I love the nutritious tweeks on such a classic comfort food.

  7. Tried this one. I was out of mushrooms so substituted it for tuna instead- My god- the burst of flavours in your mouth is just fantastic!Absolutely amazing recipe. Thanks honey

  8. @Danya - wow, I wouldn't have thought of using tuna. So what spices did you end up adding. That's a great idea. Glad you enjoyed it. Thanks for sharing.

  9. I did not change much of the spices actually-stuck with your recipe mostly [did not want to get too ambitious ;)], except I added a dash of hot chilli sauce and used rosemary instead of thyme- (somehow I like the favour of rosemary with chicken and fish). It simply tasted amazing!

  10. Hi- I mostly stuck to your recipe (did not want to get too ambitious!). I just added a dash of thai chilli sauce and used rosemary instead of thyme- somehow I love the flavour of rosemary with chicken or fish. My husband is the biggest fan of Tuna sandwiches and a tough critic and he can literally live on these. Thanks again :)

  11. I really love the sound of these. Cheese and onions are a favourite of mine, adding mushrooms and butter - now you really talking magic.

  12. Caramelized onions and mushrooms are one of the best combinations out there, love this!


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