Adjust rack to upper and lower positions and preheat oven to 425 degrees. (TIP: Preheat oven with a baking sheet inside for extra-crispy potatoes.) Wash and dry all produce. Cut potatoes into 1-inch-thick wedges. Halve, peel, and mince shallot until you have 11/2 TBSP. Pat steak dry with a paper towel and let come to room temperature.

In a large bowl, toss potatoes with a large drizzle of oil, 1/2 TBSP spice blend (we sent more), salt, and pepper. Arrange in a single layer on a lightly oiled baking sheet. Roast on upper rack until browned and crisp, 25-30 minutes, flipping halfway through.

Place stock concentrate, 1/2 cup water, and truffle zest in a medium microwavesafe bowl. Microwave on high until steaming, 1-2 minutes. Stir to combine. Set aside. Toss green beans on another baking sheet with a drizzle of oil. Season with plenty of salt and pepper. Roast on lower rack to desired doneness, 10-15 minutes.

Heat a drizzle of oil in a large pan over medium-high heat. Season steak all over with plenty of salt and pepper. Add to pan and cook to desired doneness, 3-7 minutes per side. Remove from pan and set aside to rest. Wipe out any burnt bits in pan.

Reduce heat under pan to medium and add 1/2 TBSP butter. Once melted, add minced shallot. Cook, tossing, until softened, 1-2 minutes. Pour in stock mixture and bring to a simmer. Let reduce by half, 3-5 minutes. Remove pan from heat and add sour cream and another 1/2 TBSP butter, whisking until smooth and combined. Taste and add more butter, if desired.

Divide steak, potatoes, and green beans between plates. Spoon sauce over steak and serve.