Adjust rack to top and middle positions and preheat oven to 425 degrees. Wash and dry produce.

Dice potatoes into ½-inch pieces. Zest and quarter lemon. Halve, peel, and mince half the shallot (whole shallot for 4 servings). Strip thyme leaves from stems until you have 1 tsp (2 tsp for 4), leaving remaining sprigs whole.

Toss potatoes on a baking sheet with a drizzle of oil, salt, and pepper. Roast on middle rack, tossing halfway through, until tender and crisped, 20-25 minutes.

Meanwhile, trim and discard bottom 1 inch from asparagus; toss on a second baking sheet with a large drizzle of olive oil, salt, and pepper.

Roast on top rack until lightly browned and tender, 10-12 minutes.

Carefully toss with a squeeze of lemon juice and a pinch of lemon zest to taste.

While veggies roast, pat steak* dry with paper towels; season with salt and pepper.

Rinse shrimp* under cold water and pat dry with paper towels.

Heat a drizzle of olive oil in a large pan over medium-high heat. Add steak and cook to desired doneness, 3-6 minutes per side. Turn off heat; transfer steak to a cutting board. Wipe out pan.

Heat a large drizzle of olive oil in same pan over medium-high heat. Add shrimp and season with salt and pepper. Cook, stirring occasionally, until opaque and cooked through, 3-4 minutes.

Turn off heat; transfer shrimp to a medium bowl and cover to keep warm. Wipe out pan.

Heat same pan over medium-high heat. Add 1 TBSP butter and minced shallot; cook until butter has melted and shallot is softened, 1-2 minutes.

Stir in demi-glace, whole thyme sprigs, and ¼ cup water (⅓ cup for 4 servings). Bring to a simmer and cook until sauce is slightly reduced, 2-3 minutes. Remove pan from heat; remove and discard thyme sprigs.

Stir in crème fraîche until smooth. Add lemon juice to taste and season with salt and pepper.

Thinly slice steak against the grain.

Divide steak, shrimp, potatoes, and asparagus between plates. Spoon lemon-thyme sauce over steak and shrimp. Sprinkle with thyme leaves and serve with any remaining lemon wedges on the side.