Start by gathering all items on your kitchen counter. Wash the mushrooms, and slice them thickly. Chop the onions and julienne the bell peppers. Having everything prepped makes the cooking process smoother, like a well-rehearsed play.

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the onions, sprinkle with a pinch of salt, and cook for about 5 minutes until they turn translucent and start to caramelize. Stir them occasionally; we want some lovely golden edges.

Once the onions are ready, add the sliced mushrooms to the skillet. Sauté for another 8-10 minutes, or until they are golden brown and have released their moisture. The kitchen should start smelling fantastic!

Next, toss in the julienned bell peppers. Cook everything together for about 5 more minutes, until the peppers are tender. Stir in the soy sauce, Worcestershire sauce, garlic powder, and Italian seasoning, and let those flavors meld together for a couple of minutes.

In a small bowl, mix the cornstarch with a tablespoon of water to create a slurry. Add this to the pan, stirring quickly to incorporate. It will help bind the filling and add a bit of creaminess.

Preheat your oven to 350°F (175°C). Slice the toasted sub rolls lengthwise, but don’t cut all the way through. Place the rolls on a baking sheet and layer with the mushroom filling from the skillet. Top each with a slice of smoked provolone.

Pop the baking sheet in the oven for about 10 minutes, or until the cheese is melted and bubbly. You want that glorious cheese to stretch when you take a bite!