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Grilled Cheese Sandwich with Hamakua Mushrooms & Balsamic Caramelized Onions

Grilled Cheese Sandwich with Caramelized Balsamic Onions & Hamakua Mushrooms


Sniff, sniff… “Oh-my-dog! That is caramelized onions and grilled cheese I’m smelling!”

My sense of smell is so fine tuned I sometimes scare myself at what I can pick up. Actually, sometimes the smells are scary all of their own.

It has been a few months since I sniffed this drool-worthy fragrance in the air of a Kailua parking lot, visions of grilled cheese sandwiches with caramelized onions dancing in my head since then.


Better late than never, I finally got around to making one. And it was as good as I had tasted it in my imagination. No, it wasn’t. It was better! I am now wondering about the wisdom of writing these posts while hungry, like I am right now, and all I have to nibble on are some almonds and pumpkin seeds leftover in my trail mix jar. I am heading into town for an appointment in about an hour and, on my way back, I am stopping to pick up some Tako Yaki at Shirokiya; hence my decision to stick to trail mix residues now and save my hunger for later.


Back to the sandwich: when shopping for ingredients, I decided to pick up a piece of brie and some emmenthaler, but you can use any cheese of your choice, as long as it is real cheese. Please, none of those fake, pre-melted, pre-sliced, super processed, super packaged, dare-we-still-call-them “cheeses”! The onion used is a sweet Maui onion, the mushrooms are from the Hamakua coast on the Big Island, and the loaf of bread from the best bakery on O’ahu: Fendu Boulangerie in Manoa Marketplace, Honolulu. Other than the cheeses, this was very locavore of me.




You would call this a panini, I know, and it is time that I cleared something up. In Italian, panini (plural) and panino (singular) are the general words for an edible made by bread filled with something, so basically a generic sandwich and not necessarily a hot grilled (or pressed) one as the word got somehow translated to mean here in the U.S. It can also mean simply the bread roll (with nothing inside) you buy at a panetteria (bread bakery), the root of said word being pane (bread).


I am sure panini sounds more exotic, like gelato instead of ice cream even if they are basically the same, but, but, but…. well, it is incorrect. In Italy, a grilled sandwich is called a panino caldo – literally a hot sandwich. If you go to a bar there and ask for panini, first they are going to assume you want more than one, then you will be asked with what (filling) and whether you want it hot or cold.

Aaaahhh, now that I have set the record straight I feel much better. Am I being a nit-picking, pompous bore? Too bad! *wink*
As a consolation, I can assure you that these misspellings, misinterpretations and odd uses of non-native words happen on the other end as well. I have seen business signs in Italy making well-intentioned but hilarious misuses of misspelled English words.



makes 4


– largish, good quality loaf of crusty bread of choice, or 4 single mini loaves or rolls

– 200 gr. (7 oz.) Emmenthaler cheese, sliced

– 200 gr. (7 oz.) Brie cheese, sliced

– 360 gr. (ca. 13 oz.) Hamakua or other flavorful mushrooms of choice (Porcini would be ideal of course)

– 360 gr. (ca. 13 oz.) onion (1 large)

– 2 garlic cloves, peeled, halved and cored

– 2 Tablespoons extra-virgin olive oil

– 1 teaspoon sugar

– 3 Tablespoons good quality, preferably aged, Italian Balsamic vinegar

– 125 gr. (1 stick) unsalted butter

– sea salt

– freshly ground black pepper




1. Slice the mushrooms a little thick so as to have consistency inside the sandwich. In a sauté pan heat the 2 Tablespoons extra-vigin olive oil with the 2 garlic cloves. Add the sliced mushrooms, season with salt and pepper and flip a few times to stir (or use a wooden spoon or spatula to stir). Reduce the heat to medium-low, cover with a lid and let cook for a few minutes. Remove the lid, stir a couple more times and raise the heat to medium-high for the last couple of minutes so the mushrooms color and crisp a little. Remove from heat and set aside. If you won’t be using the mushrooms right away, allow them to cool to room temperature then place in a covered container in the refrigerator.


2. Slice the onion(s) in the desired thickness, though you really don’t want slices thicker than those in the image above. Heat 1-2 Tablespoons of butter in a sauté pan, add the onions, season with salt and pepper and flip a couple of times to stir (or use a wooden spoon or spatula). Let cook on medium heat for a couple of minutes, then sprinkle with the teaspoon of sugar and stir again. Add the Balsamic vinegar and stir again. Allow to cook a few more minutes until tender and lightly caramelized. Be careful to avoid burning the onions or they will taste unpleasantly bitter. Remove from heat and set aside. Like with the mushrooms, if you won’t be using the onions right away, let them cool to room temperature then store them covered in the refrigerator.


Steps 1 & 2 can be completed 1-2 days ahead of use if needed.


3. Place the remaining butter in a small saucepan and gently melt on low heat. Heat a grill pan on the stove on medium heat, or – if you have one – preheat a “panini” press.

Slice the bread loaf into thick slices. You will need, of course, 8 slices, 2 for each sandwich.  Using a pastry brush, brush both sides of the bread slices with the melted butter. Start adding the fillings on four of the slices: spread some caramelized onions on the bottom, then the sliced Brie cheese, then the mushrooms, then the slices of Emmenthaler. Top with the other slices of bread and place on the grill pan, pressing down with a metal spatula. The bread will need to toast without burning and the filling will need to heat up and the cheese melt, so keep the heat on medium and reduce if necessary. Flip the sandwiches over to toast both sides.

When done, move the sandwiches to a cutting board and slice in half diagonally using a serrated knife. Serve immediately with a side of choice, maybe a salad or grilled vegetables.

Do you know what else would be good in this sandwich: Kalua pig shreds.


Grilled Cheese Sandwich with Hamakua Mushrooms & Balsamic Caramelized Onions


What is your favorite sandwich? And where have you had your best one?

I am not a burger eater, except very rarely, but once in a while I still think of the amazing burgers a friend an I had at a restaurant called Wild Toucan just outside of Sedona, AZ. The restaurant is no longer there, unfortunately, so I will have to find new wonderful restaurants on my next visit. Any suggestions?


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This recipe was originally published on May 14, 2013 in my Food Journey blog which is now being integrated into this one.


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  • Sonia (foodiesleuth)03/23/2015 - 12:32 pm

    Oh, my dog, indeed!
    This elevates the simple childhood favorite grilled cheese sandwich to gourmet status.
    Sounds absolutely ONO, Monica!ReplyCancel

    • Monica Schwartz03/23/2015 - 12:37 pm

      It is, Sonia! Easy to make, too. Though, like all good sandwiches, you have to prepare a few things to have on hand. 🙂ReplyCancel

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