Portobello Mushroom Bun Burgers with Guacamole

Portobello Mushroom Bun Burgers with Guacamole makes a delicious and healthy bunless burger recipe and tops it off with a perfect homemade guacamole. 

Portobello Mushroom Bun Burgers - Primavera Kitchen

Welcome to the second day of bunless burger week here at Primavera Kitchen where I’m sharing 5 Low-Carb Bunless Burger Recipes. Today, it’s the Portobello Mushroom Bun Burgers recipe and I’m sure you’ll enjoy it just because this recipe is AMAZING!

All these bunless burger recipes are and they will help you to stay on your diet during the whole summer since all these recipes are whole30, low-carb, paleo and gluten-free. The first recipe was this Spinach Sauce Bunless Burger that is to die for. The spinach sauce is so creamy with homemade mayo, spinach and avocado. Yum! In this post I also talked about how to know the safe internal temperature for your burgers. So if you have questions about that you definitely should check it out. There’s also my Whole30 Bunless Turkey Burger Recipe, Easiest Guacamole Recipe, and Easy Low-carb Bunless Burgers Recipe!

Before jumping to the recipe post I just would like to ask you one thing. If you are re-creating one of these bunless burger recipe, don’t forget to use the hashtag #bunlessburgerweek on Instagram, because I would love seeing your bunless burger recipes too 😉

So today I brought to you this Portobello Mushroom Bun Burgers with Guacamole that it’s simply a traditional hamburger using Portobello mushrooms as the bun. Cool, right? On top of that, these burgers are special because of the guacamole that adds much more flavor to this recipe.

Portobello Mushroom Bun Burgers - Primavera Kitchen

How to clean Portobello mushroom:

This is something very simple to do, but very important step to have a delicious mushroom bun since they tend to come a bit dirty from the stores. You are just going to do a quick cleaning.

  • First, you’re going to gently twist off the stem of each mushroom. The stem is delicious too, so I recommend to save it to sauté and add in your omelette or frittata for example.
  • Then, hold the mushroom cap in one hand and using a spoon, scrape out all the gills from the underside of the Portobello mushroom cap. The gills in my opinion are not great to eat, so you can discard them. Now they are ready to grill. Simple and easy!

How to grill Portobello mushroom:

Now that your mushrooms are clean and ready to cook you need to marinate them before you grill them. Doing this first will make the mushroom buns much more flavorful.

  • First, you will place all the ingredients for the Portobello Mushroom Buns in a small bowl and mix everything well to combine.
  • Then, you will add the cleaned mushroom caps in the bowl and coat them with the olive oil mixture and let stand for 1 hour.
  • Now, oil the grill or grill pan and bring the heat to medium.
  • Add the Portobello to the grill and cook for 4 minutes or so. Using tongs, carefully flip the mushroom to the other side and grill for more 4 minutes.

Portobello Mushroom Bun Burgers - Primavera Kitchen

How to shape the perfect burger patties:

Alright, here is a good way to shape your burger patties easily.

  • First, divide your mixture of ground meat and spices in 6 equally amount.
  • Second, grease your hands with a little bit of olive oil. This will avoid the meat to stick on your hands.
  • Third, shape the burger patties in a ball shape using your hands and place them on a baking sheet line with parchment paper.
  • Finally, using your four fingers gentle tap on the burger shape balls until they get flat and 1 inch thick. Then, fix the edges with your hands since the side of the burger may crack or break apart. All done and ready to grill.

Let’s jump to the recipe and make this Portobello Mushroom Bun Burgers with Guacamole recipe!

Portobello Mushroom Bun Burgers with Guacamole

Portobello Mushroom Bun Burgers with Guacamole makes a delicious and healthy bunless burger recipe and tops it off with a perfect homemade guacamole. 
4.34 from 3 votes


For the Guacamole

  • 1 avocado
  • 1/3 cup red bell pepper - finely chopped
  • 2 tablespoons diced tomatoes
  • ½ red onions - chopped
  • 1 garlic clove - minced
  • 1 tablespoon lime juice
  • Salt and black pepper
  • 1 tablespoon fresh cilantro - chopped (you can skip this ingredient if you don’t like cilantro)

For the Burger

For the Portobello Mushroom Buns

  • 2 tablespoons olive oil
  • Salt and black pepper
  • 1 garlic clove - minced
  • 8-12 Portobello Mushroom - stems and gills removed

For Serving

  • Slices of red onions - tomatoes, cooked bacon and microgreen leaves or any other green leaves you prefer to serve.


  • Make the spinach sauce: Add avocado in a bowl and mash it with a fork. Add all the ingredients and stir well. Set aside.
  • Place all the ingredients for the mushroom buns in a bowl, except for the mushrooms. Mix well. Add the mushroom into the olive oil mixture bowl and coat them well. Set aside for about 1 hour. Place “buns” on grill and let them cook for 4-5 minutes.
  • To make the burger, combine all ingredients, except the olive oil, in a large bowl. Mix everything well to combine and using your hands divide the mixture into 4-6 burgers.
  • Heat the olive oil in a non-stick grill pan (or simply cook your burger in a BBQ) over a medium-high heat. Cook the burger for 3-5 minutes on each side, or until reach 145°F for medium-rare or 160°F for well-done. Set them aside.
  • To build each burger, top one Portobello mushroom guacamole, patty burger, more guacamole, two slices of red onions, 2 slices of bacon, 2 slices of tomatoes and some microgreen or leaves. Top with second Portobello mushroom ban.
Serving: 1/6, Calories: 317kcal, Carbohydrates: 14g, Protein: 22g, Fat: 18g, Saturated Fat: 5g, Cholesterol: 73mg, Sodium: 470mg, Fiber: 5g, Sugar: 8g

If you make this recipe, follow @primaverakitchen on Instagram, snap a photo and hashtag it #primaverakitchen. I'd love to see what you're making!

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Portobello Mushroom Bun Burger with Guacamole - Primavera Kitchen