Marinated Portobello Sandwiches
I tend to get out to at least one of the many Oktoberfest celebrations that happen here in Durham each fall, but in 2024 I didn't and I found myself craving the pretzel and beer cheese combo I commonly enjoy at these festivities. So I made it a priority to get that into my October Meatwave, the only problem was neither of those are grilling recipes, so I started to ponder how could I take those two things and work them into something that would output a recipe I could share with y'all. The answer came to me with these marinated portobello sandwiches.
For the longest time I really hated portobellos, probably because they were sold to me as a meat equivalent and I wasn't buying it. Once my tastes began to broaden and I was able to get out from under my various aversions, I understood the meat comparison more since portobellos do have the heft to make them entire meal worthy, and while I wouldn't equate their earthy flavor with meat, I can see how one would call them "meaty."
Since these were destined for sandwiches with the big flavors of caramelized onions and beer cheese, I devised a very savory marinade for the portobellos that comprised of soy sauce, lemon juice, Dijon mustard, brown sugar, garlic, pepper, and oil. I set my cleaned mushroom caps in the marinade and let them sit overnight in the fridge, which was a bit too long as a few of the shrooms came out overly soggy, so I adjusted the time down accordingly in the final recipe.
With the deep savory and lightly pungent flavor of the marinade, I wanted to bring more sweetness to the party to balance out the final sandwich and decided caramelized onions were the way to do that. There's probably other routes you can go if you don't want to spend 30-plus minutes making these onions, but I love them so much that the time doesn't bother me and I actually make way more than I need because I'll just eat them with a spoon if I have leftovers.
For the beer cheese, I wanted to improve upon a recipe I did for Serious Eats a long time ago that turned out well for me, but had some more mixed result for others. I've been making this Martha Stewart mac and cheese recipe for years, and that cheese sauce always turns out perfect, so I modeled my process after that, starting with making a roux and slowly adding milk and beer to create a thick base.
From there, I added the cheese in, one handful at a time, until the sauce was just slightly thinner than I wanted, knowing it would thicken up a bit off the heat. For the additional seasoning I added in Dijon, hot sauce, garlic powder, onion power, and miso paste, which was a vegetarian-friendly substitute for the Worcestershire I would normally add.
When it got near to showtime, I fired up the grill, arranged the coals in a two-zone fashion, with all the charcoal situated on one side of the grate. I then placed the portobellos on the cool side of the grill and covered. I like to start the shrooms gill-side up because you can easily see how much moisture has been pulled out since it pools in the center of the cap. When I see a lot of water in there, I know the mushrooms are close to being done and I'll flip them and move them over the hot side of the grill.
The second portion of the cook is about getting a little extra color and char in spots to give the mushrooms a good grilled flavor. Since the portobellos had lost a lot of moisture by this point, it only took a few minutes to achieve this.
Once done, I set each mushroom cap on top of a pretzel roll that I had adorned with small handfuls of arugula first. I then spooned on some caramelized onions and beer cheese, which needed to be reheated first, and it was then time to chow down.
I was all too happy to get the pretzel and beer cheese combo I was craving, but I got so much more with these sandwiches. The portobellos were extra hearty with the marinade giving them a deeper, more savory flavor which would make a description of "meaty" feel even more apt than usual. The heartiness of them was matched well with the super sweet onions, creamy beer cheese, and peppery arugula. They felt so apt for the season that I could even see them fitting right into an Oktoberfest menu, even though they're not traditional fare.
