2largeonionswhite, yellow, and red all work; 3 small onions
16ouncesbaby bella or white mushroomsthickly sliced
1red bell pepper, slicedsliced
1green bell peppersliced
46" sub rolls
To make the caramelized onions: In a large skillet, heat 1 tablespoon olive oil over medium-high heat. Saute the sliced onions for 6-8 minutes, until lightly browned. Sprinkle with ½ teaspoon salt and lower the heat to medium-low. Stir the onions only every 9-10 minutes. They're ready when golden brown and sweet, which can take up to an hour.
In a medium skillet, heat 1 tablespoon of olive oil over medium-high heat. Add the mushrooms and peppers and saute until the mushrooms release most of their juices, about 7-8 minutes.
Sprinkle mushrooms with soy sauce and oregano. To thicken the mushrooms and their juices, sprinkle with 1 tablespoon of flour, stirring to brown.
Melt the provolone cheese by placing each slice over a section of mushrooms and peppers. Cover the pan with a lid to melt.
Scoop the melted cheese and mushrooms onto a toasted sub roll. Top with caramelized onions and enjoy!
Leftovers and reheating: Store leftovers refrigerated in a closed container. Best within 3-4 days. Reheat in the microwave in just 1-2 minutes, or reheat on the stove-top over medium heat.
Toasting the buns: Spread the buns with melted butter and garlic salt and toast at 350F for 3-4 minutes. This is the method that I use for meatball subs.