- 4 large portabella mushroom caps, gills scraped and halved horizontally
- Salt and pepper
- Juice of ½ small lemon
- 1 cup flour
- 3 eggs, beaten
- 1 cup panko
- 1 cup grated Parmigiano-Reggiano cheese
- 2 tablespoons flat-leaf parsley, finely chopped
- 1 teaspoon granulated garlic
- 1 teaspoon crushed red pepper flakes
- 1 tablespoon fresh thyme, chopped
- Olive oil, for shallow frying mushrooms and a drizzle for beef patties
- 1½ pounds ground beef (80/20)
- Sliced provolone cheese, 1 or 2 slices per burger (or layer with crispy mushrooms if making vegetarian sandwiches)
- ½ cup ketchup
- 2 tablespoons aged balsamic vinegar or balsamic drizzle
- 3 tablespoons Fabanaise or mayonnaise
- Romaine or iceberg lettuce, chopped
- 4 soft sesame seed burger buns
- White onion, chopped and rinsed
- Giardiniera, drained and pulse-chopped in food processor
Dress the portabellas with salt, pepper, and lemon juice, and let stand a few minutes. Coat mushrooms in flour, then egg, and then panko mixed with parm, herbs, garlic, and red pepper flakes. Heat about 1/8 inch oil in large skillet over medium to medium-high heat and brown the mushrooms 2-3 minutes on each side, and drain on wire rack. Keep warm in 275˚F oven.
Heat a cast-iron skillet over medium-high to high heat. Form 4 loose patties of beef. Add a drizzle of oil to the skillet, add meat, season with salt and pepper, and press with a spatula; brown and flip patties, 5-6 minutes. Top with cheese to melt.
Combine ketchup, balsamic and mayo for the sauce.
Build burgers: bun bottom, lettuce, onions, Giardiniera relish, burger patty, 2 crispy portabellas, sauce and bun top.