Adjust racks to top and middle positions and preheat oven to 450 degrees. Wash and dry all produce. Cut potatoes into ¼-inch-thick rounds. Strip thyme leaves from stems; roughly chop leaves until you have 2 tsp (4 tsp for 4 servings). Finely chop pecans or crush in their bag with a heavy pan or rolling pin.

Toss potatoes on a lightly oiled baking sheet with a drizzle of oil, half the chopped thyme, salt, and pepper. Roast on top rack until browned and tender, 20-25 minutes total. (We’ll add more to the oven after 12 minutes.)

Meanwhile, place 2 TBSP butter (3 TBSP for 4 servings) in a medium microwave-safe bowl. Microwave until melted, 30 seconds. Let cool slightly, then stir in pecans, panko, remaining chopped thyme, and a pinch of salt and pepper. In a small bowl, combine honey, mustard, and mayonnaise.

Pat trout dry with paper towels; season with salt and pepper. Drizzle skin sides with oil; rub to coat. Once potatoes have roasted 12 minutes, place trout skin sides down on a second baking sheet. Evenly spread tops with a thin layer of honey mustard sauce (reserve remaining sauce for serving), then mound with pecan mixture, pressing firmly to adhere. Transfer potatoes to middle rack and place trout on top rack. Roast until crust is golden brown and trout is cooked through, 10-12 minutes.

Meanwhile, quarter lemon. Halve, core, and thinly slice apple. In a large bowl, combine mixed greens, apple, a large drizzle of olive oil, and as much lemon juice as you like. Season with salt and pepper.

Divide trout, potatoes, and salad between plates. Drizzle trout with remaining honey mustard sauce and serve.