Portobello Keto Cheeseburger

It's a simple fact that buns don't work on low-carb diets like keto.

The average hamburger bun has about 30 grams of carbs in it, which is more than half the number you want to aim for on keto each day [*].

A simple substitute? Use two portobello mushroom caps instead. That's a simple and delicious way to make a healthy keto cheeseburger with only a fraction of the carbs.

Portobello mushrooms are loaded with B vitamins, minerals, and fiber. And there's only 3 grams of net carbs per serving in this recipe, which makes it perfect for any low-carb nutrition plan.

This burger recipe isn't scant on delicious toppings, either. It's loaded with bacon, cheddar cheese, and fresh veggies, so you'll still get an incredibly satisfying meal.

See if this doesn't become one of your go-to burger recipes going forward—we know you're going to love it. 

Ingredients Needed

  • Portobello mushroom caps
  • Ground beef 
  • Bacon
  • Cheddar cheese
  • FBOMB Olive Oil
  • Mixed greens
  • Spices (garlic powder, onion powder)

Tips for Making Burgers

Here are some tips to make sure your burgers turn out hot and juicy and don't end up overcooked!

  • Use 80/20 beef: This is the ideal meat-to-fat ratio that helps lock in flavor without adding any unnecessary calories to your meat.
  • Form patties gently: Avoid mashing the burger meat together so the patties don’t get tough. 
  • Don’t salt your patties until after they’re formed: Salt and pepper are essential for giving it flavor and helping grill marks form. Mixing salt into the meat can make the burger less juicy.
  • Be generous with salt and pepper: Great for forming that perfect crust and bringing out the natural flavor of the beef. A healthy dose of each is the way to go!
  • Put a dent in the middle of your patty: This helps the patty hold its shape as it cooks and prevents it from falling apart or cooking unevenly.
  • Use a meat thermometer: The best way to cook your burgers to desired doneness is to use an internal or infrared thermometer. Here's a rough temperature guide:
    • 120°F (49°C) and below for rare (red/raw in the center)
    • 130°F (54°C) for medium-rare (pink and warm)
    • 140°F (60°C) for medium (totally pink, starting to dry out)
    • 150°F (66°C) for medium-well (grayish-pink, significantly drier)
    • 160°F (71°C) and above for well-done (completely gray, very little moisture)

    Keto-Friendly Burger Toppings

    You'll want to avoid ketchup and BBQ sauce and most breaded toppings like fried onion rings due to carbs and excess sugar.

    But you’ll still have plenty of delicious options, like:

    • Bacon
    • Avocado
    • Tomato
    • Lettuce
    • Onions (raw or caramelized)
    • Sautéed mushrooms
    • Cheese
    • Mayonnaise
    • Mustard
    • Hot sauce
    • Pesto

    See? No real restrictions and plenty of yummy things to put on top of your burger patties!

    Ingredient Spotlight: Portobello Mushrooms

    Not privy to the benefits of portobello mushrooms? Let's run down some of the nutrition facts and how to best prepare these fungi.

    Health Benefits

    One serving of portobello mushrooms is [*]:

    • Loaded with B vitamins
    • High in minerals like calcium, magnesium, phosphorus, copper, and selenium
    • Rich in fiber, with almost 3g per serving
    • Perfect for a low-carb diet (Only 4g of carbs per serving!)

    Ways to Cook Portobello Mushrooms

    When cooking your portobello mushrooms for this keto cheeseburger recipe, throw them right on the grill. 

    If you're serving a big meal, you can do them ahead of time in the oven, but grill marks really add some serious flavor right to the caps of these mushrooms.

    You can also sauté your portobellos, but that's probably best for other recipes. You don't want the caps to get too soft so that they can hold the burger and all the toppings. In this case, grilling is the way to go.

    How to Clean and Prepare Portobello Mushrooms

    To make sure your portobellos are clean and ready to be cooked [*]:

    • Wet a paper towel and rub down the outside of your mushrooms. Scrub both the cap and stem to get any dirt or debris off them.
    • Give the portobellos a few minutes to dry. If you're in a rush, lightly dry them with another paper towel.
    • Gently remove the stem by gripping it from the bottom and gently rotating the cap. This should help it come off in one piece.
    • Scrape away the black gills underneath. The flesh should be a white color when you're done.
    • Brush with oil and toss on the grill!

    Other Keto Recipes You’ll Love

    Recipe Information:

    • Yield: 1
    • Serving size: 1 burger with 2 mushroom caps
    • Prep time: 30 minutes
    • Cook time: 15 minutes


    • 2 large portobello mushroom caps, stems and gills removed
    • 1 packet (2 tablespoons) FBOMB Olive Oil
    • 1 tablespoon balsamic vinegar
    • 2 teaspoons salt, divided
    • 1 teaspoon black pepper, divided
    • 2 slices bacon
    • 4 ounces ground beef
    • 1/2 teaspoon garlic powder
    • 1/2 teaspoon onion powder
    • 1/2 teaspoon Worcestershire sauce
    • 1 slice cheddar cheese (or cheese of your preference)
    • 1 slice tomato
    • 1/4 cup mixed greens or arugula
    • 1 tablespoon reduced-sugar ketchup


    1. Put the portobello mushroom caps in a bowl or shallow dish and add the olive oil, balsamic vinegar, and half of the salt and pepper; marinate for at least 30 minutes.
    2. Cook the bacon in a skillet at medium-low heat until crispy, flipping over a couple of times to evenly cook each side. Set aside for later use as a topping.
    3. Turn the grill on medium-high heat (about 200-300°F). In a bowl, mix together the ground beef, garlic powder, onion powder, and Worcestershire sauce. 
    4. Gently form into a patty, about as wide as the portobello “buns.” Season each side with the remaining salt and pepper. 
    5. Put the portobello mushrooms and the burger on the grill (you may need to do this separately if you are preparing multiple servings). Cook the portobello mushrooms for about 3-4 minutes on each side until they are soft and heated through. The burger will take about 5-6 minutes on each side for medium-rare. Put the cheese on the burger for the last minute of cooking to melt.
    6. Assemble your burger with the bacon and the rest of the toppings between the portobello mushrooms.

    Nutrition Facts Per Serving:

    Calories: 771

    • Fat: 67g
    • Protein: 38g
    • Total Carbohydrates: 4g
    • Fiber: 1g
    • Sugar Alcohol: 0g
    • Net Carbohydrates: 3g


    • Fat: 78%
    • Protein: 20%
    • Carbohydrates: 2%


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