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

Dice potatoes into ½-inch pieces. Place in a medium pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, 10-15 minutes.

Reserve 1 cup potato cooking liquid, then drain and return potatoes to pot. Cover to keep warm (you’ll finish the potatoes in Step 5).

While potatoes cook, trim green beans if necessary. Peel and mince or grate garlic. Quarter lemon.

Toss green beans on a baking sheet with a drizzle of oil, half the garlic, salt, and pepper. Roast on top rack for 10 minutes.

Once green beans have roasted 10 minutes, remove sheet from oven. Carefully sprinkle almonds over green beans.

Return to top rack and roast until green beans are tender and almonds are browned and fragrant, 2-5 minutes more.

While green beans roast, pat barramundi* dry with paper towels. Season all over with salt and pepper.

Heat a large drizzle of oil in a large, preferably nonstick, pan over medium-high heat. Add barramundi, skin sides down, and cook until skin is crispy, 4-5 minutes. Flip and cook until barramundi is opaque and cooked through, 2-3 minutes more.

Turn off heat; transfer to a plate. Wipe out pan and let cool 2 minutes.

To pot with potatoes, add sour cream and mash until smooth and creamy, adding splashes of reserved potato cooking liquid as needed. Taste and season with salt and pepper if desired.

Melt 2 TBSP butter (4 TBSP for 4 servings) in pan used for barramundi over medium-low heat. Add basil paste, remaining garlic, and juice from one lemon wedge (two wedges for 4).

Cook, whisking constantly, until fully incorporated and warmed through, 1-2 minutes.

Divide mashed potatoes, barramundi, and green beans amandine between plates in separate sections. Drizzle basil sauce over barramundi and serve with any remaining lemon wedges on the side.