Grilled portobellos with bacon, Swiss, roasted red pepper, and garlic mayo

Give me summer or give me death. - Patrick Henry. 

Or was it liberty? Don't care because summer is a kind of liberty in and of itself. This burger-like sandwich feels most at home in the park or on the porch, at a BBQ, alongside some corn on the cob and/or mac salad and/or potato salad. Portobello burgers aren't just for vegetarians, and I made sure of it with the addition of bacon (although they easily can be, sans bacon). Mushrooms + bacon + Swiss is an age-old combo (maybe not, although I'm sure Patrick Henry would have been down to clown around), and I even took it up a notch with some roasted red pepper, grilled onions, fresh basil, and garlic-y mayo. 

You've got to go big or go home with this guy. Don't skimp on the garlic mayo, don't use a cold or dry bun, and don't throw away the extra marinade juice. All of it is needed to keep this portobello burger dripping with flavor.

Grilled portobellos with bacon, Swiss, roasted red pepper, and garlic mayo

Marinade inspired from Serious Eats
Yields 4 sandwiches
4 Portobello mushrooms, stems removed, rinsed/scrubbed clean, and drained/dried
¼ cup balsamic vinegar
¼ cup plus 1 tsp olive oil, divided
Juice of half a lemon
1 T Dijon mustard
½ tsp salt, plus a little more for sprinkling at the end
Freshly cracked black pepper
4-6 slices bacon (leave this out for a vegetarian option)
4-6 large outer rings of a sweet onion (sliced about ½ inch thick)
4 Brioche rolls
Butter for rolls
4 slices Swiss cheese
Garlic mayonnaise (recipe below), to be divided among sandwiches
2 roasted red peppers, sliced into four equal pieces
Fresh basil leaves, enough to cover each sandwich
Grill pan for stovetop grilling (or a real grill)

Garlic mayonnaise

⅓ cup mayonnaise
1 clove garlic, grated on a microplane/zester
Pinch salt
Freshly cracked black pepper

Begin by making the garlic mayonnaise at least a half hour before using. Combine ingredients in a small bowl and stir together. Cover and store in fridge to let flavors really develop.   

Then marinate the mushrooms, also at least a half hour before beginning to cook. Whisk together balsamic vinegar, ¼ cup olive oil, lemon juice, Dijon, ½ tsp salt, and pepper. Place mushrooms in a shallow baking dish, stem side up, and pour marinade over them. Let sit for at least a half hour (longer is better), spooning marinade over them now and then to coat well.

Cook the bacon (either in the oven or on a griddle) to desired doneness and set aside on a paper towel to soak up excess grease.

Heat a grill pan over medium-low heat. Toss onion rings in a small bowl with 1 tsp oil, and a pinch of salt and pepper. Grill the onions for a few minutes per side, just to take the rawness out of them and give them a sweet, charred flavor. Remove from pan and set aside.

Increase heat of grill pan to medium, and grill the mushrooms, stem side up, over medium heat for about 8-10 minutes, and then flip them and repeat with other side. Cook until soft and tender to the touch, like a steak would be. As they cook, baste them with extra marinade.

Pull mushrooms from grill pan and set on aluminum foil. Immediately wrap the foil around them to keep heat in and let the juices get re-absorbed.

While the mushrooms rest, wipe out the grill, butter the buns (I even like to spread a little of the garlic mayo on them), and grill them. When done, spread a tablespoon or so of garlic mayo on each half of every bun—you really can’t add too much—and set aside.

Turn broiler to Low with the rack in the top position. Open up foil package of mushrooms, and place mushrooms on bottom halves of buns, topping with any extra juices from the foil. Top each with a slice of Swiss. Place on a baking sheet and put under broiler until cheese is melted—don’t take your eyes off of it! It will only take a minute or two. Remove from oven when cheese is melted and buns are warm.

Then layer on roasted red pepper, bacon, onion, a couple fresh basil leaves, and the top half of the bun (that should already be slathered with garlic mayo). Sprinkle with a little extra salt and pepper and voilà! A juicy, flavorful portobello burger to, dare I say, rival the real thing.