Step 1

Adjust rack to top position and preheat oven to 425 degrees. Bring a medium pot of salted water to a boil. Wash and dry all produce. Trim and thinly slice scallions, separating whites from greens. Trim and halve Brussels sprouts lengthwise; toss on one side of a baking sheet with a drizzle of oil, salt, and pepper. Roast on top rack for 10 minutes (you’ll add more to the sheet then).

Step 2

Once water is boiling, add couscous to pot. Cook until al dente, 6-8 minutes. Drain, then place empty pot over medium heat. Add truffle butter and scallion whites; cook, stirring, until softened, 1 minute. Stir in cooked couscous until evenly coated. Turn off heat; cover until ready to serve.

Step 3

Meanwhile, pat beef dry with paper towels; season with salt and pepper. Sprinkle with half the Steak Spice (all for 4 servings), pressing to adhere. Heat a large drizzle of oil in a large pan over medium-high heat. Add beef and cook until a crust forms, 2-3 minutes per side (it’ll finish cooking in the next step). Turn off heat.

Step 4

Once Brussels sprouts have roasted 10 minutes, remove sheet from oven. Add beef to empty side. Roast on top rack until Brussels sprouts are browned and tender and beef reaches desired doneness, 10-12 minutes. (TIP: Beef may finish before Brussels sprouts.) Remove from oven; let beef rest for 5 minutes.

Step 5

Meanwhile, wipe out pan used for beef; return to medium-high heat. Stir in stock concentrate and 1/4 cup water (1/3 cup for 4 servings). Simmer until slightly thickened, 2-3 minutes. Reduce heat to low and whisk in mustard. Turn off heat; stir in sour cream. (TIP: If you like, add any resting juices from beef and cook sauce until reduced, 1-2 minutes more.) Season with salt and pepper. TIP: If sauce gets too thick, stir in hot water 1 TBSP at a time until it reaches a drizzling consistency.

Step 6

Fluff couscous with a fork; stir in Parmesan and half the scallion greens. Season with salt and pepper. Divide couscous, Brussels sprouts, and beef between plates. Spoon sauce over beef. Sprinkle with remaining scallion greens and serve.