Add the butter, sliced onion, and soy sauce to your slow cooker. Layer the mushrooms, garlic, poblano peppers, bell pepper, oregano, and a pinch of salt and pepper on top. Stir lightly to combine.

Cook the mixture on low for 4 hours or on high for 2 to 3 hours, until the vegetables are tender and infused with flavor.

Preheat your oven to 400°F. Stuff the cooked vegetable mixture into the hoagie rolls, place a slice of provolone cheese on top, and wrap each sandwich in parchment paper. Bake directly on the oven rack for about 5 minutes, or until the cheese is melted and bubbly. Serve immediately, with Yum Yum Sauce on the side if desired.

Begin by melting the butter in your pressure cooker on the sauté setting, then stir in the onion and soy sauce. Secure the lid and cook under high pressure for 2 minutes. Release the pressure using the quick-release method.

Add the mushrooms, garlic, peppers, oregano, salt, and pepper. Return the lid to the pot and pressure-cook for another 4 minutes. Use the quick-release method again to release pressure.

Assemble and bake the sandwiches as described in the slow cooker method, ensuring the cheese melts evenly.

Heat the butter in a large skillet over medium-high heat. Add the sliced onion and sauté for about 5 minutes, stirring often, until softened.

Stir in the soy sauce, then add the mushrooms, garlic, poblano peppers, and bell pepper. Cook for 10 minutes, stirring occasionally, until the vegetables are caramelized and tender. Add the oregano, along with salt and pepper, and cook for another minute before removing from heat.

Fill the hoagie rolls with the vegetable mixture, top each with provolone cheese, and bake in the oven as detailed in the slow cooker method.