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

Peel garlic. Peel and dice potatoes into ½-inch pieces. Trim green beans if necessary.

Place garlic cloves in center of a small piece of foil; drizzle with oil and season with salt and pepper. Cinch into a packet and place on a baking sheet. Roast on middle rack for 10 minutes (you’ll add more to the sheet then).

Meanwhile, place potatoes in a medium pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, 15-20 minutes. Reserve ½ cup potato cooking liquid (¾ cup for 4 servings), then drain. Return potatoes to pot and cover to keep warm.

While potatoes cook, in a medium bowl, combine panko, half the Parmesan, 1 TBSP oil (2 TBSP for 4), salt, and pepper.

Pat trout* dry with paper towels and season all over with salt and pepper. Place on a plate; drizzle skin sides with oil; rub to coat. Arrange skin sides down on plate.

Evenly spread tops of fish with a thin layer of half the mustard. Mound with panko mixture, pressing firmly to adhere.

Once garlic has roasted 10 minutes, remove sheet from oven;  carefully add trout to one side (keep garlic packet on sheet).

Toss green beans on empty side with a drizzle of oil, salt, and pepper. Return to middle rack; roast until veggies are tender and trout is browned and cooked through, 10-12 minutes. (For 4, toss green beans on a second sheet; roast green beans on middle rack and trout and garlic on top rack.)

In a small bowl, combine half the vinegar, half the cream sauce, remaining mustard, and 1 tsp sugar (all the vinegar and 2 tsp sugar for 4).

Heat a small pan over medium. Add cream sauce mixture. Cook, stirring occasionally, until thickened, 2-4 minutes. Remove from heat; stir in 1 TBSP butter (2 TBSP for 4). Season with salt and pepper. Cover.

To pot with potatoes, add roasted garlic with its oil, remaining cream sauce base, remaining Parmesan, and 1 TBSP butter (2 TBSP for 4 servings). Mash with a potato masher until smooth and creamy, adding splashes of reserved potato cooking liquid as needed. Season with salt and pepper.

Divide trout, green beans, and mashed potatoes between plates. Drizzle trout with creamy mustard sauce and serve. TIP: If sauce has thickened too much, add a splash of water and stir to thin.