Portobello Mushroom Sandwich

This Portobello Mushroom Sandwich is the BEST! Big, rich and meaty this vegetarian burger will make you a believer of a meatless meal! It can be made in the slow cooker or Instant Pot and it's super easy.
Course Vegetarian
Cuisine American
Prep Time 15 minutes
Cook Time 4 hours
Total Time 4 hours 15 minutes
Servings 2 sandwiches
Calories 712
Author Souper Chef Deb


  • 2 portobello mushrooms
  • 1 16 oz package pre-sliced mushroom
  • 1 red bell pepper
  • 1/2 red onion
  • 1/2 cup bbq sauce - use your favorite
  • 1 teaspoon salt
  • 1/2 teaspoon pepper
  • healthy pinch red pepper flakes
  • Coleslaw
  • 1/2 head cabbage
  • 2 carrots
  • 1/2 red onion
  • 1/2 cup mayonnaise
  • 2 tablespoons cider vinegar
  • 2 tablespoons honey
  • salt and pepper to taste


  • Clean the portobello mushrooms, remove the stem & fins, place in the slow cooker. Top with the pre-sliced mushrooms.
  • Slice the bell pepper, remove the seeds and slice into strips. Remove the outer peel from the onion and slice into strips. Place into the slow cooker with the mushrooms.
  • Season the vegetables with salt, pepper & red pepper flakes, top with bbq sauce. Put the lid on the slow cooker & cook on high for 4 hours or low for 6.
  • While the meal is cooking, make the cole slow. Thinly slice the cabbage, clean & shred the carrots (I use a box grater.), thinly slice the onions, place in a large bowl.
  • Mix the coleslaw dressing together - it will be quite thick, but that's how you want it. Mix the dressing with the vegetables, refrigerate until ready to use.
  • Toast the burger buns.
  • Assemble and enjoy!


Calories: 712kcal | Carbohydrates: 78g | Protein: 7g | Fat: 43g | Saturated Fat: 6g | Cholesterol: 23mg | Sodium: 2349mg | Potassium: 1258mg | Fiber: 11g | Sugar: 59g | Vitamin A: 12475IU | Vitamin C: 167.1mg | Calcium: 147mg | Iron: 2.3mg