Adjust racks to top and middle positions and preheat oven to 450 degrees. Wash and dry produce.

Cut potatoes into ½-inch-thick wedges. Halve, peel, and thinly slice onion. Halve, core, and thinly slice green pepper. Trim and slice mushrooms into ¼-inch-thick pieces (skip if your mushrooms are pre-sliced!).

Toss potatoes on a baking sheet with a large drizzle of olive oil, half the Fry Seasoning (you’ll use the rest in the next step), salt, and pepper.

Roast on top rack until golden brown and tender, 20-25 minutes.

Meanwhile, heat a large drizzle of olive oil in a large pan over medium-high heat. Add onion, green pepper, and remaining Fry Seasoning; cook, stirring occasionally, until softened and lightly browned, 5-7 minutes. Season with salt and pepper.

Turn off heat; transfer to a medium bowl. Wipe out pan.

While veggies cook, in a small bowl, combine mayonnaise and mustard; season with salt and pepper.

Slice baguettes lengthwise, stopping before you cut all the way through. Place baguettes (cut sides up) on a second baking sheet.

Toast on middle rack until lightly golden, 3-5 minutes.

Heat a large drizzle of olive oil in pan used for veggies over medium-high heat. Add mushrooms and cook, stirring occasionally, until browned and crispy, 5-7 minutes.

Season with half the Steak Spice (all for 4 servings) and salt; cook, stirring, until fragrant, 30 seconds.

Stir in stock concentrate and a splash of water. Cook until liquid has evaporated and mushrooms are saucy, 1-2 minutes.

Return veggies to pan; stir to combine.

Keeping baguettes on sheet, spread cut sides with half the Dijon mayo; fill with as much of the veggie mixture as will fit, then sprinkle with mozzarella. (TIP: For an extra-saucy situation, use all the Dijon mayo on the hoagies.) Return sheet to oven until cheese melts, 2-3 minutes.

Divide hoagies and potato wedges between plates. Serve with remaining Dijon mayo on the side for dipping.