Wash and dry all produce. Preheat broiler to high. Place a large pot of salted water over high heat. Peel potatoes, then slice into thick rounds (about 1/3-inch thick). Add to pot. Bring to a boil and cook until easily pierced by a fork, about 10 minutes. Drain.

Meanwhile, halve, peel, and dice onion. Thinly slice mushrooms. In a small bowl, combine cheddar, panko, and a drizzle of oil. Chop chicken into 1/2-inch pieces. TIP: Now is a good time to check on the potatoes.

Heat a drizzle of oil in a large pan over high heat (use a broiler-safe pan if you have one). Add chicken and cook, tossing, until browned and nearly cooked through, 4-5 minutes. Season with salt and pepper. Remove from pan and set aside.

Add onion, mushrooms, and a drizzle of oil to same pan over mediumhigh heat. Cook until softened, 5-6 minutes. Return chicken to pan along with stock concentrate, peas, and 1/2 cup water. Bring to a boil and cook until liquids are reduced by half, 3-4 minute

Remove pan from heat and stir in sour cream. (TIP: If your pan isn’t broiler-safe, transfer contents to a small metal or broiler-safe baking dish at this point.) Arrange potato slices on top of filling in a layer. Sprinkle panko mixture evenly over top.

Place pan under broiler and broil until top is golden brown and bubbly, 3-5 minutes. Divide pie between plates and serve.