Caramelized Onion Breakfast Sandwiches

The only thing better than brunch is brunch with loved ones! This is a great recipe for the next time you are hosting a breakfast get-together at your place, or if you need a dish to take over to friends. Is anyone planning a Mother’s Day brunch this week??? If so, take note, this might be the dish to make.

But what are these? Croissant breakfast sandwiches, inspired by a breakfast sandwich I had at Civil Coffee a couple months ago (yes, I’m still thinking about it!). A buttery, flaky croissant gets filled with flavorful soft scrambled cheesy eggs. Mmmm. Is your mouth watering yet? And yes, these are simple but still very special. Probably the ingredient that sets them off the most is the caramelized onions. The recipe below will make six sandwiches, but you could easily cut each sandwich in half to serve more if you’ve got a brunch buffet or potluck happening.

Caramelized Onion Breakfast Sandwiches, makes six

1 large white onion
2 tablespoons butter, divided
1 tablespoon vegetable stock or water
1 oz mushrooms or other veggies (bell pepper would be good here too)
6 eggs
2 tablespoons milk
4 oz. shredded cheese (I used Monterey Jack but cheddar would be great too.)
6 croissants
poppy seeds or sesame for garnish

First make the caramelized onions. In a large pan or skillet melt one tablespoon of butter over medium/low heat. Add the chopped onion and cook for 40-50 minutes until very brown and jam-like. Turn off the heat and stir in a tablespoon of vegetable stock or water. Stir well, making sure to scrape up and incorporate the bottom layer that may be clinging to the bottom of the pan. Salt, and now they are ready for use.

In the photos above, I actually doubled the amount of onion I was needing (I caramelized two onions instead of one) because I like to make extra when I go to the trouble so I can use them in other things throughout the week. You can store caramelized onions in a covered bowl or container in the refrigerator for at least a week, but maybe more. You can also make them the night before you plan to make these breakfast sandwiches so it’s easy to throw everything together just before it’s time to serve them.

When you are ready to make the sandwiches, whisk together the eggs and milk. In a large skillet, add a little oil and cook the mushrooms (or other veggies) along with the caramelized onions until everything is nice and warm. Then add the eggs to the pan and stir until soft scrambled. You want them to be slightly undercooked here because they will cook a bit more in the oven, so don’t be afraid to leave them a bit runny.

Slice the croissants in half and fill with the eggs and top with cheese, arranged in a rectangle baking dish. Add the croissant tops, and then brush with melted butter and top with poppy seeds. Bake at 350°F for 5-6 minutes, just until the cheese looks melted.

Serve along with fresh fruit or a breakfast salad. Enjoy! xo. Emma

Note: If you are a meat eater, you could totally substitute the mushrooms for cooked, chopped bacon here. If that’s, like, your thing. 🙂

Credits // Author and Photography: Emma Chapman. Photos edited with the NEW A Beautiful Mess actions.
  • Great work! However, I would recommend red onions as they are sweeter than white

  • Good for you for telling the truth about how long it takes to caramelize onions–40-50 minutes, and not 15 like SO many recipes say! 🙂 This looks so tasty!

  • This is looks amazing, I know whats for lunch today!

  • Yum!! Just had carmelized onions on a sandwich, but I’ve never made them myself. I’m going to have to give this a try!

  • I’m a firm believer that caramelized onions and mushrooms make everything better! Even as a meat eater, I wouldn’t change a thing about this recipe. Those umami flavors and the protein-rich eggs are a perfect match!

  • My goodness, this sounds and looks incredible. I love breakfast foods and this beaut just shot to the top of my ‘to try’ list!


  • They look so delicious!
    I used to do a similir recipe when I was in college: croissants filled with ham + cheese + a little honey on top and then everything into the oven so the cheese will melt! SO YUMMY!!
    Btw I love the pink mug!!

    Hugs from France! 🙂

  • They sound delicious ! And the pics make me so hungry 😉

  • This sounds amazing! I would love to have this for breakfast everyday please <3

  • OMG these look soooooooo good. And EASY. Like, I could make them while sipping mimosas without any trouble.

  • i made up a big jar of carmelized onions myself a couple of weeks ago with honey, balsamic and with bacon in it! then i spent the next week adding it to everything its so versatile and adding it makes everything feel fancier and foodie! ( also FRENCH ONION SOUP!! ) it added a really nice flavor to pasta dish, tacos, pulled pork, and a pizza with goat cheese spinach, roasted cherry tomatoes ….. always make up a bunch extra!
    that croissant is making my mouth water!!! it looks heavenly!!!

  • Yummy! Definitely need a second breakfast right now!

  • This looks really, really good – I love the suggestion with fruits or a salad too!

    Charmaine Ng | Architecture & Lifestyle Blog

  • Perfect for Mother’s day this weekend! Love a savory AND easily-made-veggie-friendly dish. Yum!

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