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

Dice potatoes into ½-inch pieces. Pick and finely chop fronds from dill.

Cut broccoli into bite-size pieces if necessary. (Save potatoes for another use.)

Toss potatoes on a baking sheet with a drizzle of oil and a pinch of salt and pepper.

Roast on top rack, tossing halfway through, until lightly browned and tender, 20-25 minutes.

Swap in broccoli for potatoes; roast 12-15 minutes.

While potatoes roast, pat chicken* dry with paper towels; season all over with salt and pepper.

Heat a drizzle of oil in a large pan over medium-high heat. Add chicken and cook until browned and cooked through, 5-7 minutes per side. Transfer to a cutting board to rest.

Pat salmon* dry with paper towels; season with salt and pepper. Heat a drizzle of oil in a large, preferably nonstick, pan over medium-high heat. Cook salmon (skin side down) until skin is crisp, 5-7 minutes, then flip and cook until cooked through, 1-2 minutes more. Transfer to a plate to rest.

While chicken cooks, trim green beans if necessary; toss on a second baking sheet with a drizzle of oil and a pinch of salt and pepper.

Roast on middle rack until tender, 10-12 minutes.

Heat pan used for chicken over medium heat. Stir in stock concentrate, 2 TBSP water (4 TBSP for 4 servings), and as much chopped dill and mustard as you like.

Remove pan from heat; stir in sour cream and 1 TBSP butter (2 TBSP for 4), scraping up any browned bits from bottom of pan. Season with salt and pepper. TIP: If sauce seems too thick, add more water 1 tsp at a time until it reaches a drizzling consistency.

Slice chicken crosswise.

Divide chicken, potatoes, and green beans between plates. Drizzle sauce over chicken. Garnish with any remaining chopped dill and serve.

Divide salmon, potatoes, and broccoli between plates and drizzle with sauce. Garnish with any remaining chopped dill if desired and serve.