Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 450 degrees. Wash and dry produce.

Trim green beans if necessary; toss in one oven-ready tray with a drizzle of oil, salt, and pepper. (For 4, divide green beans between two trays, using a drizzle of oil in each tray.)

In a small bowl, combine panko with a drizzle of oil (large drizzle for 4), salt, and pepper.

Pat salmon* dry with paper towels; season with salt and pepper. Drizzle skin sides with oil; rub to coat.

Place salmon, skin sides down, in remaining oven-ready tray. (For 4 servings, divide between two remaining trays.) Evenly spread tops with Dijon mustard; mound with panko mixture, pressing firmly to adhere. Reserve bowl.

Place trays side by side on top rack (be sure your oven has preheated!); bake until green beans are tender and salmon is cooked through, 10-15 minutes. (For 4, bake salmon on top rack and green beans on middle rack, swapping rack positions halfway through.)

Meanwhile, wash and dry bowl used for panko. Combine smoky mustard and mayonnaise in same bowl; stir in water 1 tsp at a time until mixture reaches a drizzling consistency.

Meanwhile, when salmon has 5 minutes remaining, halve and toast ciabatta. Spread with half the garlic herb butter.

Halve each ciabatta half on a diagonal. (For 4 servings, halve each of the four ciabatta halves on a diagonal.)

Once green beans are done, carefully toss with remaining garlic herb butter.

Divide salmon, green beans, and garlic bread between plates. Drizzle smoky mustard sauce over salmon and serve.