Portobello burgers are a proven hit with vegans, vegetarians and omnivores alike! These juicy sandwiches are made with hearty mushroom caps slathered in a zippy Dijon mustard sauce. Cook them up in the oven or on the grill!
Clean the mushrooms and remove the stems. Scrape out the gills with a spoon.
Whisk the Dijon mustard, olive oil, vinegar, maple syrup and garlic together in a small bowl. Taste-test and adjust any seasonings to your liking.
Brush the Dijon mixture all over the outsides of the mushroom caps. Reserve any extra.
To bake: Preheat the oven to 400°. Arrange the mushrooms on a baking sheet, stem sides up, and bake for 10-12 minutes, until tender.
To grill: Lightly oil your grill and build a medium flame. Place the mushrooms directly on the grill and cook for about 4 minutes on each side, until slightly charred and tender.
Remove the mushrooms from the oven or grill and allow them to cool for a few minutes. Sprinkle with salt and pepper to taste.
Stuff the mushrooms into buns and top with any reserved sauce or additional Dijon mustard and toppings of choice. Serve.