Adjust rack to top position and preheat oven to 425 degrees. Place garlic herb butter in a large bowl; bring to room temperature. Wash and dry all produce. Place peppercorns in a zip-close bag; crush with a rolling pin or a heavy-bottomed pan. Zest and quarter lemon (for 4 servings, zest 1 lemon; quarter both). Halve, peel, and mince shallot until you have 2 TBSP (4 TBSP for 4). Halve baguette lengthwise.

Place 1 TBSP plain butter (2 TBSP for 4) in a small microwave-safe bowl; microwave until softened, 10 seconds. (TIP: Do so in 5-second intervals, checking in between, to avoid melting.) Stir in garlic powder (start with 1/4 tsp; add more to taste), salt, and pepper. Toss green beans on a baking sheet with a large drizzle of olive oil, salt, and pepper. Roast on top rack until browned and tender, 12-15 minutes. Cover to keep warm.

Meanwhile, pat steak dry with paper towels and season all over with salt and pepper. Heat a drizzle of olive oil in a large pan over medium-high heat. Add steak and cook to desired doneness, 5-7 minutes per side. Turn off heat; transfer to a cutting board. Wash out pan.

Rinse shrimp and pat dry with paper towels; season all over with salt and pepper. Heat another drizzle of olive oil in pan used for steak over medium heat. Add shrimp and cook until opaque and cooked through, 3-4 minutes. Turn off heat; transfer shrimp to large bowl with garlic herb butter. Toss until thoroughly coated. Cover to keep warm. Wipe out pan.

Melt 1 TBSP plain butter in same pan over medium heat. Add minced shallot and cook, stirring, until slightly softened, 1-2 minutes. Add stock concentrates, 1/4 cup water (1/3 cup for 4 servings), and 1/2 tsp crushed peppercorns (1 tsp for 4; be sure to measure). Simmer until slightly thickened, 2-3 minutes. Turn off heat. Stir in another 1 TBSP plain butter (2 TBSP for 4). Season with salt and more peppercorns if desired.

Spread baguette with garlic spread. Toast in oven (use a baking sheet or place directly on oven rack) until golden, 3-5 minutes. Halve on a diagonal. Toss green beans with both lemon zest and juice to taste. Slice steak against the grain. Divide garlic bread, green beans, and steak between plates. Spoon pan sauce over steak; top with shrimp. Serve with any remaining lemon wedges and pan sauce on the side.