Adjust rack to top position and preheat oven to 425 degrees. Wash and dry all produce. Trim and thinly slice scallions, separating whites from greens. Quarter lime. In a small bowl, combine sour cream, mayonnaise, and wasabi to taste. Add water 1 tsp at a time until sauce reaches a drizzling consistency. Set aside.

Heat a drizzle of oil in a small pot over medium-high heat. Add scallion whites and cook until softened, 1 minute. Stir in rice, 3/4 cup water (11/2 cups for 4 servings), and a big pinch of salt. Bring to a boil, then cover and reduce to a low simmer. Cook until rice is tender, 15-18 minutes. Keep covered off heat until ready to serve.

Pat tilapia dry with paper towels. Rub each fillet with a drizzle of oil; season with salt and pepper. Place on a baking sheet; roast for 8 minutes (it’ll finish cooking in step 5). Remove from oven. Meanwhile, in a large bowl, combine tempura mix, 1/3 cup cold water (2/3 cup for 4), and 1 tsp salt (2 tsp for 4) until smooth. (TIP: If mixture is too thick, add water 1 TBSP at a time until it reaches a pancake-batter-like consistency.) Stir green beans into batter until coated.

Heat a 1/3-inch layer of oil in a large, heavy-bottomed pan over medium-high heat. Once oil is hot enough that a drop of batter sizzles when added to the pan, working in batches, add coated green beans in a single layer. Cook, turning occasionally, until golden brown, 5-7 minutes. Transfer to a paper-towel-lined plate and season with salt.

Once green beans are done, heat broiler to high. Brush tops of tilapia with hoisin. Return sheet to oven and broil until glaze is tacky and fish is cooked through, 2-3 minutes.

Fluff rice with a fork; season with salt and pepper. Divide rice, tilapia, and green beans between plates. Top fish and green beans with sesame seeds and scallion greens. Serve with wasabi sauce and lime wedges on the side.