Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce.

Using the tip of a spoon, remove and discard black gills from undersides of portobello mushrooms; trim any large stems if necessary. Slice tomato into ¼-inch-thick rounds.

Drizzle both sides of each mushroom with 2 tsp olive oil; rub to evenly coat. Season all over with half the Fry Seasoning, salt, and pepper. Place mushrooms, top sides down, in oven-ready tray (divide between two trays for 4 servings). Evenly sprinkle mushrooms with mozzarella.

In a small bowl, combine panko, remaining Fry Seasoning, a large drizzle of olive oil, salt, and pepper.

Sprinkle breadcrumbs on top of each mushroom, and lighly press down. Tightly cover pan with aluminum foil; cook mushrooms until tender, 14-16 minutes.

Once tender, remove foil and continue to cook until golden brown on top, about 5 minutes TIP: Watch carefully to avoid burning.

Evenly sprinkle panko mixture over mushrooms, lightly pressing to adhere. Tightly cover tray with aluminum foil. Bake on top rack (be sure your oven has preheated!) until mushrooms are tender, 14-16 minutes. (For 4 servings, bake two trays side by side on top rack.)

Once mushrooms are tender, remove foil and cook until cheese and panko are golden brown, about 5 minutes more. TIP: Watch carefully to avoid burning!

While mushrooms bake, in a second small bowl, combine mayonnaise and smoky mustard.

Halve and toast buns.

Divide sandwiches between plates along with salad. Drizzle more ranch on salad if desired.

Once mushrooms are done, in a large bowl, toss mixed greens with half the dressing; season with salt and pepper.

Spread cut sides of buns with smoky mustard sauce; fill buns with sliced tomato, mushrooms, and crispy fried onions.

Divide sandwiches and salad between plates. Drizzle remaining dressing over salad if desired and serve.