2 tablespoons EVOO (extra-virgin olive oil)
1 medium portobello mushroom cap, gills scraped off (see Tip), finely chopped
1 1⁄2 pounds ground beef chuck
1 green bell pepper, seeded and chopped
1 small onion, chopped
3 to 4 cloves garlic, finely chopped
1 teaspoon dried oregano or marjoram
1 teaspoon crushed red pepper flakes
Kosher salt and black pepper
2 tablespoons tomato paste
1⁄2 cup (a couple of glugs) red wine
1 cup beef stock or 1 (10.75-ounce) can beef consommé
2 tablespoons Worcestershire sauce
1 cup canned crushed tomatoes or tomato sauce
1⁄4 cup flat-leaf parsley leaves, finely chopped
6 ciabatta rolls or 12 slider rolls, split
4 tablespoons (1⁄2 stick) unsalted butter, softened
Grated Parmigiano-Reggiano or pecorino Romano cheese
Shredded fresh basil leaves
Preheat the broiler.
Heat the EVOO, 2 turns of the pan, in a deep skillet or a heavy-bottomed pot over medium-high heat. Add the mushroom and brown 5 minutes. Add the beef and cook, breaking it up with a wooden spoon, until browned, 7 to 8 minutes. Add the bell pepper, onion, garlic, oregano or marjoram, and red pepper flakes; season with salt and pepper and cook 5 minutes. Stir in the tomato paste, then add the wine and cook another minute. Add the beef stock, Worcestershire sauce, and crushed tomatoes or tomato sauce. Stir in the parsley and simmer a few minutes to thicken.
While the filling is simmering, toast the rolls: Brush the cut sides with butter, top with some cheese, and broil to brown.
Spoon the filling onto the roll bottoms and top with a little basil. Set the roll tops in place.
TIP: The gills on the underside of a Portobello mushroom cap can turn sauces and gravies a dark, muddy brown. To keep your sauce nice and clean, just scrape off the gills with a teaspoon. You don’t need to worry about the gills if you’re cooking the caps whole.