Make the sauce for the finished burgers. In a small bowl, combine plain Greek yogurt, olive oil, minced garlic cloves, dijon mustard, dried basil and salt. Mix well, then refrigerate (covered) until ready to use.
Wipe mushrooms clean with a damp cloth. Remove stems and gills from underside of mushroom. Clean the gills out by carefully running a small spoon around the underside of the mushroom. Discard gills. Make marinade for mushrooms by mixing together olive oil, balsamic vinegar, dried basil, garlic powder and a pinch of salt. Pour marinade over prepared portobello mushrooms, turning to cover; let them sit in marinade for 20 minutes (with mushroom top face down in marinade most of the time).
Heat a skillet on medium-high. Lightly brush skillet with the olive oil. Add mushrooms and red onion slices to hot skillet. Cook mushrooms 4 minutes per side, until tender. Cook onions until tender and lightly browned.
While mushrooms cook, split and lightly butter each cut side of hamburger buns. Grill them, butter side down in a skillet, until toasted and lightly browned.
To assemble burgers, spread a Tablespoon of the dijon sauce on the bottom side of a toasted bun. Top with cooked red onion, then put the cooked mushroom on top of onions with the top (smooth side) down. Sprinkle with bleu cheese crumbles, then cover with lettuce leaf. Top with bun, and it's ready to eat!
Nutrition Facts
Portobello Bleu Cheese Burger
Amount Per Serving (1 burger)
Calories 532Calories from Fat 360
% Daily Value*
Fat 40g62%
Saturated Fat 11g69%
Cholesterol 28mg9%
Sodium 547mg24%
Potassium 511mg15%
Carbohydrates 31g10%
Fiber 3g13%
Sugar 8g9%
Protein 11g22%
Vitamin A 2745IU55%
Vitamin C 3.4mg4%
Calcium 192mg19%
Iron 2.7mg15%
* Percent Daily Values are based on a 2000 calorie diet.