Wash and dry all produce. Preheat oven to 425 degrees. Trim Brussels sprouts and halve through base. Cut potatoes in half. Toss potatoes with a drizzle of olive oil on a baking sheet. Season with salt and pepper. Roast in oven until tender, 20-25 minutes total (we’ll add more to the sheet after 10 minutes).

Toss Brussels sprouts with a drizzle of olive oil and a pinch of salt and pepper in a medium bowl. Once potatoes have roasted 10 minutes, remove from oven and give them a toss. Add Brussels sprouts to sheet. Return sheet to oven and continue roasting until both are tender and crisped, 10-15 minutes more.

Halve, peel, and thinly slice shallot. Trim, then thinly slice mushrooms. Finely chop parsley.

Heat a drizzle of oil in a large pan over medium-high heat. Pat pork dry with a paper towel. Season all over with salt and pepper. Add to pan and cook to desired doneness, 4-6 minutes per side. Remove from pan and set aside.

Add mushrooms and shallot to same pan. Cook, tossing occasionally, until softened, 3-5 minutes. Stir in stock concentrate and 1/4 cup water, scraping up any browned bits from bottom. Bring to a boil, then remove from heat. Stir in sour cream and parsley. Season to taste with salt and pepper.

Divide pork, Brussels sprouts, and potatoes between plates. Drizzle sauce over pork, making sure to add mushrooms, and serve.