Mise en Place
- Preheat oven to 425 degrees F (if using)
- Wash and dry fresh produce.
- Remove the stems from the mushrooms.
- Peel and mince garlic.
- Peel, pit, and slice avocado (if using).
- Measure out the ingredients.
Prepare Mushroom Seasoning
- In a bowl, whisk together the vinegar, salt, pepper, garlic and oil.
- Pour over the mushroom caps and make sure they are coated evenly.
- Place them on a baking tray, rounded side down.
- Let sit for about 15 minutes. Don’t rinse the bowl, because you’ll use any oil and vinegar residue to dress the spinach.
Prepare the Portobello (choose one cooking method)
- Stove Top/grill cooking:
- Prepare a medium-hot grill or heat a heavy skillet over medium-high heat, or preheat an electric grill or panini pan on medium-high.
- Season the mushrooms as desired with salt and pepper.
- Place the mushrooms on the hot grill or pan, rounded side down.
- Cook for about 6-8 minutes, depending on thickness, until lightly browned and moist.
- Turn over and cook for another 6 minutes. Turn over for a minute to reheat the top, then flip back over and place the cheese on top.
- Continue to cook until the cheese melts.
- Panini grill:
- Heat to high and cook 6-8 minutes.
- Open the grill and place the cheese on top. Wait for it to melt.
- Oven cooking:
- Preheat oven to 425°F.
- Place mushrooms on the baking tray with rounded side down.
- Place baking tray in the oven and roast for 15-20 minutes, until cooked through.
- Remove tray from oven and flip mushroom caps.
- Place cheese on rounded side. Allow to melt.
Prepare the Burgers
- In a medium bowl, toss spinach in oil and vinegar to lightly dress.
- Place a mound of spinach on the bottom half of each hamburger bun and place the mushrooms, rounded side up, on top of the spinach.
- Top with your choice of condiments.