Wash and dry produce.

If desired, peel potatoes. Dice potatoes into ½-inch pieces. Place in a medium pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, 12-15 minutes.

Reserve ½ cup potato cooking liquid; drain and return potatoes to pot. Keep covered off heat until ready to mash in Step 4.

While potatoes cook, trim and thinly slice mushrooms (skip if your mushrooms are pre-sliced!). Quarter lemon.

Pat chicken* dry with paper towels. Place between two large pieces of plastic wrap; pound with a mallet or heavy-bottomed pan until about ½ inch thick. Season all over with salt and pepper.

Sprinkle chicken all over with flour, pressing to adhere; shake off any excess.

Heat a drizzle of oil in a large pan over medium-high heat. Add coated chicken; cook until browned and cooked through, 4-6 minutes per side. (For 4 servings, you may need to cook in batches.) Turn off heat; transfer chicken to a cutting board. Wipe out pan.

Return pot with drained potatoes to low heat. Add half the sour cream, half the garlic powder, and 1 TBSP butter (2 TBSP for 4 servings). (You’ll use the rest of the sour cream and garlic powder in the next step.)

Mash until smooth and creamy, adding splashes of reserved potato cooking liquid as needed. Season with salt and pepper. Keep covered off heat until ready to serve.

Heat a drizzle of oil in pan used for chicken over medium-high heat. Add mushrooms; season with remaining garlic powder and pepper. Cook, stirring, until softened, 2-4 minutes.

Stir in stock concentrate and ¼ cup water (⅓ cup for 4 servings). Bring to a boil, then reduce to a low simmer. Cook, stirring, until slightly thickened, 2-3 minutes.

Remove from heat. Stir in remaining sour cream and 1 TBSP butter (2 TBSP for 4) until melted and combined. Season with salt and pepper.

In a large bowl, toss arugula with a drizzle of olive oil, a squeeze of lemon juice, salt, and pepper until evenly coated. Taste and season with more salt and pepper if desired.

Divide chicken, mashed potatoes, and salad between plates.

Spoon mushroom sauce over chicken and mashed potatoes. Sprinkle Parmesan over salad. Serve with remaining lemon wedges on the side.