Marinated Portobello Mushroom Burger with Yuca Fries

Recipe posted in: Lunch/Dinner
portobello mushroom burger

When you think of a keto diet, you rarely think of a plant-based meal that’s free of meat. However, we’re proving that even a low carb diet can include vegetarian dishes that are packed with flavor and fiber! Thick, meaty portobello mushroom patties are soaked in a garlicky marinade to replace the typical beef burger in this fun meatless meal. We serve them up on low carb lettuce wraps with a side of homemade yuca fries that are baked to crispy perfection.

mushroom burgerWhile most veggie burgers are high in carbohydrates and filled with processed ingredients, this healthy mushroom burger keeps things simple. The main ingredient is a hearty portobello mushroom. Infuse these mushroom patties with flavor by cleaning them thoroughly and removing the stems before marinating. Place them into a bowl and add the marinade, which includes a flavorful blend of olive oil, red wine vinegar, Dijon mustard, garlic, rosemary, erythritol sweetener, salt and pepper. Ensure the mushrooms are fully coated before placing them into the refrigerator for at least 15 minutes (or up to four hours) to marinate.

What is a burger without a side of fries? While the burgers are marinated, whip up some quick and easy fries made from yuca root (also known as cassava). Peel the root, cut it into half inch wedges and toss them with olive oil and sea salt. Arrange the fries in a single layer on a sheet pan, leaving at least a half inch of space between each wedge. Bake the fries at 400 degrees for 30 minutes, flipping halfway through the cooking time. mushroom burger

While the fries are baking, remove the mushrooms from the refrigerator and marinade. Heat olive oil in a large pan over medium heat and cook the mushrooms for about five minutes per side. To serve, place each mushroom on a romaine leaf and top with a slice of cheese. Arrange the yuca fries on the side of the plate and feel free to throw on some of your favorite burger toppings. Try out sliced red onions, pickles, avocado and tomatoes. You can even add a small amount of mustard, mayonnaise or unsweetened ketchup! Just be sure to keep track of any additions that you add by referring to our Grocery Guide.

Tasty Tip: These keto veggie burgers can also be prepared on the grill for a flavorful alternative! Check out these seven tips for healthy low carb grilling. >

One serving of these Marinated Portobello Mushroom Burgers with Yuca Fries counts as two and a half Healthy Fats and two Vegetables on your South Beach Diet program. Please note that due to the yuca fries, this recipe contains a higher amount of net carbs. If you’re on our keto friendly program, be sure to keep track of your net carb intake to keep it below 50 grams or less per day. The South Beach Diet Tracker app makes it easy to keep track of your net carbs with the handy macro tracker feature. Click here to learn more about our FREE app! >

Looking for more plant-based recipes for your keto friendly plan? Check out some of our favorite low carb creations below:

Lose weight and get healthy with a convenient meal delivery service! The South Beach Diet brings delicious keto friendly food directly to your door. Learn more about our low carb meal plans >

For even more recipes like this one, check out the book The New Keto-Friendly South Beach Diet written by the creator of the South Beach Diet, Arthur Agatston, M.D.

Phase: Weight Loss Phase, Weight Maintenance Phase

Servings: 4

Nutrition Information

  • 2.5 Healthy Fat
  • 2 Vegetables


  • 4 portobello mushrooms, cleaned and stems removed
  • 6 Tbsp. olive oil, divided
  • 2 Tbsp. red wine vinegar
  • 1 Tbsp. Dijon mustard
  • 1 garlic clove, pressed or minced
  • ¼ tsp. dried rosemary
  • 1 Tbsp. erythritol-based sweetener (granulated)
  • 1 large yuca (cassava), peeled and cut into ½-inch wedges
  • ¼ teaspoon salt
  • 4 large romaine lettuce leaves
  • 4 slices cheddar cheese


  1. Preheat oven to 400°F.
  2. Place mushrooms into a shallow dish large enough to accommodate all four of them.
  3. Whisk together ¼ cup olive oil, vinegar, mustard, garlic, rosemary, erythritol sweetener and salt and pepper to taste in a small bowl. Pour the marinade over the mushrooms, turning them to fully coat.
  4. Transfer the mushrooms to the refrigerator for at least 15 minutes (or up to 4 hours) to marinate.
  5. Toss the yuca wedges with 1 tablespoon olive oil and salt.
  6. Arrange the yuca wedges in a single layer on a sheet pan, leaving at least a half inch of space between each wedge. Bake for 30 minutes, flipping halfway through the cooking time.
  7. Remove mushrooms from marinade. Heat remaining 1 tablespoon olive oil in a large pan over medium heat.
  8. Add mushrooms to the pan and cook 4-5 minutes per side. (Alternately, they may also be cooked on a grill or grill pan.)
  9. Place each mushroom on a romaine leaf and top with a slice of cheese and your favorite burger toppings. Enjoy with a side of yuca fries.