Onions are great on burgers, but what if I told you I created the ULTIMATE onion trifecta that makes THE BEST onion burger? It takes a little time, but it’s easy to prep and you can make it ahead of time!

These killer burgers are topped with chipotle-infused caramelized onions and mushrooms as well as a smoky garlic aioli. They’re REAL good, friends — with or without a bun!

We’ll get to the burger business in a minute. First, a word about that crazy good topping you’re going to put on them.

The crown jewels of this recipe are the caramelized onions, of course.

Nothing I’ve done in the kitchen is so magical to me than taking something as pungent as a raw onion and turning it into something almost as sweet as candy with just butter, heat, and a little patience. It’s nature’s finest magic trick. *chef’s kiss*

I think it’s important to note that you do NOT need sugar to make caramelized onions. Nope. None. Onions have plenty of natural sugars — especially sweet onions.

Mouth-wateringly delicious Onion Burger

Let’s talk about the topping on these burgers.

Nothing I’ve done in the kitchen is so magical to me than taking something as pungent as a raw onion and turning it into something almost as sweet as candy with just butter, heat, and a little patience. It’s nature’s finest magic trick. *chef’s kiss*

Can caramelizing onions be considered a hobby? Just checking.

I think it’s important to note that you do NOT need sugar to make caramelized onions. Nope. None. Onions have plenty of natural sugars — especially sweet onions.

Onion Burger Ingredients

• Butter: You can also use coconut oil or ghee if you prefer.
• Onions: Preferably sweet yellow onions or Vidalia, if you can find them.
• Sea Salt and Black Pepper
• Button Mushrooms: Brown or White
• Chipotle Peppers: Just a couple from a can of chipotles in adobo sauce.
• Ground beef
• Worcestershire sauce
• Mayonnaise
• Garlic
• Buns and fixings

Best onions for caramelizing

I’d recommend using sweet onions or yellow onions over red onions or white onions. If you can find Vidalia onions, get those. They’re a little spendier, but they become incredibly sweet! (They also make the best onion rings, FYI.)

Caramelized onions have the reputation of being time consuming. You could drag out the caramelization process for an hour, if you like. But I don’t have time for that. I give them 30-40 min tops.

Do I have to use chipotle peppers?

I love the addition of the chipotle peppers — it adds some heat that works well with that sweet flavor. Not a ton of heat though, if you only use one seeded pepper.

If you really don’t want to use them, leave them out. Or add 2-3 Tablespoons of balsamic vinegar to deglaze your onions & mushrooms at the end! (Deglaze, if you don’t know, just means adding liquid at the end of sauteeing to release any crispy bits stuck to the bottom of the pan. That liquid also reduces quickly and adds some flavor to what you’re making.)

How to Make the perfect Caramelized Onions Burger

How to Caramelize Onions

Here are some tips for making quick caramelized onions:

Start out the onions on medium-high heat, then continue cooking them on medium heat until they’re dark golden brown.

Use plenty of butter/oil. I use butter or avocado oil, but you can use olive oil, too. This keeps them from sticking to the bottom of the pan or skillet and helps them develop their color. If they keep sticking, add a little water to the pan and stir to get the browned bits off the bottom. You could also use a non-stick pan to help with this.

Keep a close eye on them and stir them often.

Don’t overcrowd the pan. You can cover the bottom of the pan in a good-sized layer since they reduce quite a bit, but don’t fill the pan or skillet to the brim or it’ll take FOREVER for them to caramelize.

Adding the mushrooms helps the onions from sticking to the pan, too, since they’ll release some moisture as they cook and both will be nice and toasty brown at the end. Like that photo above. So good, right?

For the Smoky Garlic Aioli

This easy spread is just a few simple ingredients:

• Mayonnaise (I like to use avocado oil mayo to avoid seed oils)
• Worcestershire sauce or coconut aminos
• Fresh Garlic
• Sea salt

That’s it! It adds a lot of flavor and is way more interesting than regular mayonnaise.

Assembling the Onion Burgers

The burgers themselves are seasoned simply — just salt, pepper, and a glug of Worcestershire, which is my usual when I want a neutral, but flavorful burger.

Spread on some aioli and pile those caramelized onions and mushrooms high!

You could also add some cheese to those burger patties — I’d recommend pepper jack cheese or something smoked for this. Like smoked gouda.

Caramelized Onion Burger Variations

If you need this burger to be gluten or grain free, use a gluten-free bun (honestly, I have no recommendations. I’d rather go without than use a GF bun, but if you have one you like, go for it!

Or wrap it in lettuce and…. end up with a big mess. lol

Or smear some of that aioli right on the burger patty underneath the onions & mushrooms and have at it with a fork and knife.

Tips for Making the Perfect Burger With Mushrooms

• Make sure your onions are golden brown before adding the mushrooms. They’ll cook together really well, but the longer you cook the onions the better the whole thing will turn out.
• Use whatever mushrooms you prefer! If you want something with a little more mushroom flavor, try using shiitake or sliced portabello mushrooms.
• Make the topping ahead of time if you like! Just store it chilled until you’re ready to top your burgers. Toss it in a skillet to reheat it with a few tablespoons of water to keep it moist.
• Please make the aioli! Aioli is simply seasoned mayonnaise and this savory mixture makes the BEST sauce for these mushroom burgers.

More Ways to Use Sweet Caramelized Onions

Once you’ve made the best caramelized onions, you’ll want to do a lot with them! 

Did you know you can freeze them?? Just store them in a freezer bag, a freezer-safe airtight container, or if you need them in smaller-sized portions, try freezing them in ice cube trays.

Here are a few ways to use them:

French Onion Soup — I have a recipe for French Onion Soup in The Big Book of Paleo Pressure Cooking with some added beef stew meat. That sweet onion flavor is amazing in soup.

Patty Melt is basically this burger except with a thinner patty made into a grilled cheese-type of sandwich with sandwich bread.

You could add them to pizza, grilled sandwiches, casseroles (Like this BBQ Pulled Pork Spaghetti Squash Bake), over grilled meats (like my Grilled Chicken with Rosemary Caramelized Onions).

More Burger Recipes on Perry’s Plate

If you like this recipe, try another one of my burger recipes! (Apparently I have a thing for onions & mushrooms on burgers…)

Smash Burgers with Caramelized Onions & Jalapeños have a similar vibe to this recipe, but in smash burger form.

Double Mushroom Burgers with Roasted Garlic Aioli have delicious roasted mushrooms and the BEST aioli!

The Ultimate Goat Cheese Burger is one you should definitely not try if you dislike goat cheese. You have been warned.

Green Chile Turkey Burger with Guac-Ranch is my FAVORITE turkey burger!

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If you make one of my recipes, be sure to post it on social media and tag me at @perrysplate or #perrysplate so I can send you some love!

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