Adjust rack to top position and preheat oven to 450 degrees. Wash and dry produce.

Cut broccoli into bite-size pieces if necessary. Peel and mince or grate garlic. Finely chop parsley. Quarter lemon.

Toss broccoli on a baking sheet with a drizzle of olive oil, ½ tsp chili flakes (¾ tsp for 4 servings), salt, and pepper. (Use fewer chili flakes if you prefer less heat.) Roast on top rack until browned and tender, 12-15 minutes.

Meanwhile, heat a drizzle of olive oil in a small pot over medium-high heat. Add half the minced garlic; cook until fragrant, 30 seconds. Stir in couscous, stock concentrate, 1 cup water (2 cups for 4 servings), and a big pinch of salt. Bring to a boil, then cover and reduce heat to low. Cook until couscous is tender, 6-8 minutes.

Keep covered off heat until ready to use in Step 5.

While couscous cooks, rinse shrimp* under cold water; pat dry with paper towels. Heat a large drizzle of olive oil in a large pan over medium-high heat. Add shrimp, garlic powder, salt, and pepper. Cook until shrimp are pink and almost cooked through, 3-4 minutes.

Add 2 TBSP water (3 TBSP for 4 servings); cook, stirring and scraping up any browned bits from bottom of pan, until water has evaporated, 1-2 minutes.

Reduce heat to medium; add 1 TBSP butter (2 TBSP for 4), remaining minced garlic, and a pinch of chili flakes. Cook, stirring, until shrimp are cooked through and garlic is fragrant, 1-2 minutes more.

Remove pan from heat; toss shrimp with half the parsley and juice from half the lemon.

Fluff couscous with a fork; stir in remaining parsley, a squeeze of lemon juice, and a drizzle of olive oil. Season with salt and pepper.

Divide couscous between bowls. Top with shrimp and broccoli. Spoon any remaining garlic butter from pan over shrimp. Serve with a squeeze of lemon juice.