Maitake Smash Burgers with Sumac Onions

Jump to Recipe

Smash burgers are having a moment. They seem to be served on every corner of every metropolis. They have been turned into everything from tacos to salads. Smash burgers are even served fries-supreme-style over their traditional side. We have reached peak smash burger and I for one am happy to see it. Burgers, smashed or otherwise, are a perfect food. But why would I present you with a classic burger when I already have one on this site? So instead here is my vegetarian take on the smash burger. These Maitake Smash Burgers feature maitake mushrooms marinated in ras el hanout and olive oil smashed and roasted between two large baking sheets. The mushrooms are piled onto a bun slathered with a mint aioli and topped with sumac onions and fresh cucumber. It may not be your classic burger stand burger but it’s still mighty fine,  so let’s make it!

We’re going to start by mincing a couple of cloves of garlic. Transfer the garlic to a comically large bowl. I, like most people, have a mental block when it comes to using large pots, pans, bowls, etc. I guess it’s because I think they are more cumbersome to clean or they take up too much dishwasher real estate. So trust me that when I tell you to reach for a large anything it’s because there is no workaround or alternative. So have faith and put that smidgeon of garlic inside a gigantic bowl. 

With the dishware successfully over-explained, let’s move along by adding to this marinade. That is what we’re making, by the way. This will be a marinade for the maitake mushrooms, but right now it is a whisper of garlic in a cavernous bowl. Let’s remedy that by adding the zest of one lemon. Zest is great when you want the suggestion of citrus without too much acid. Next, add a heaping tablespoon of ras el hanout followed by a little salt and a whole lot of olive oil. Whisk everything together and set the marinade aside.

For those of you who are unfamiliar with ras el hanout, allow me to introduce you. Ras el hanout is a medley of spices that pops up in Tunisian, Algerian, and Moroccan cuisines. The name means “head of the shop” in Arabic and it implies that this blend is made up of the highest quality and most valuable spices the seller has to offer. 

The spices found in ras el hanout vary from blend to blend. Some shops, companies, and even families guard their ras el hanot ingredients and ratios carefully. But most blends include cardamom, cumin, clove, cinnamon, nutmeg, allspice, ginger, chili, paprika, fenugreek, and turmeric. This is the brand I used. So yeah, ras el hanot has a lot going on and it covers a lot of bases. Not bad for a single ingredient. You can use it as part of a rub for meat, poultry, or fish. Or you can stir it into couscous, pasta, or rice. But today, this particular ras el hanout is bound for a mushroom marinade.

Now, let’s put the maitake in these Maitake Smash Burgers. I was lucky enough to find this huge maitake mushroom at St. Lawerence market here in Toronto. But if you can only find more rationally sized shrooms, don’t fret. Just stock up on a few little ones and you’ll make up the difference. They might be easier to slice than this bad boy was.

Slice your mushrooms into 1/4-inch slices. Place the mushrooms in the marinade and toss to coat. Transfer to the fridge and chill for 30 minutes. Small pieces may fly off while you’re slicing the mushroom or tossing the slices in their marinade. Do not worry about that. Those little bits will turn into crispy bits after a brief turn in the oven. They add excellent texture and they turned out to be my favourite part of the sandwich. Go figure. 

 While the mushrooms are marinating, we will tackle the sumac onions because they need to hang out for a bit as well. Start by thinly slicing one red onion. You can do this with either a sharp chef’s knife or a mandolin. Pile the onion slices into a bowl and add a heaping teaspoon of sumac and half a teaspoon of salt. Give everything a toss, so the onion slices are evenly coated. Add olive oil and some white wine vinegar and toss to coat once again. Set the onions aside to soften and deepen in flavor. This is also a good time to start preheating your oven to 450°F. 

Now, let’s get the aioli going. This is by far the easiest portion of the recipe. Why? Because all you have to do is pop everything into a blender and let it do the work. So place fresh mint leaves, a minced clove of garlic, salt, lemon juice, and two egg yolks in a blender. Add olive oil and blitz until smooth and thickened. This could take a little bit. Pour the finished aioli into a bowl and chill until ready to serve. 

Okay, let’s get those mushrooms into the oven. Place a silicon mat on a large baking sheet and arrange the mushroom slices in an even layer. Place a second silicone mat on top of the mushrooms and another baking sheet of equal size. Make sure the bottom of the baking sheet is facing down. On top of the top baking sheet place a cast iron skillet. Pop the whole rig into the oven and roast for 10 minutes. Remove the frying pan, the top baking sheet, and the silicone mat. Flip the mushrooms and bake for 5 minutes more. 

All that remains is to build your Maitake Smash Burgers. So slather a bun with mint aioli and add some sumac onions. Top the onions with a few mushroom slices and top them with cucumber and more sumac onions. Place the top bun on, well, top, and serve immediately.

And that’s everything you need to know about these Maitake Smash Burgers. Loaded with sharp, tangy, and meaty flavors, this meatless wonder will delight you as much (if not more) as a classic smash burger. 

Enjoy!