Preheat your oven to 200°C / 400°F (convection) or 210°C / 410°F (conventional). Preheating ensures the oven is hot enough to finish the salmon quickly so it stays tender inside while developing a light crust on the outside.

Prepare the sweet potatoes: place the peeled and cubed 400 g sweet potatoes into a medium pot and cover with cold water by 2 cm. Add 1 teaspoon salt. Bring to a gentle boil over high heat, then reduce to a simmer and cook until very tender when pierced with a fork — about 12–15 minutes. Starting in cold water and salting it seasons the potatoes evenly and helps them cook through uniformly.

While the potatoes cook, pat the salmon fillets (340 g total) dry with paper towels. Season both sides generously with salt and a few grinds of black pepper. If skin-on, score the skin lightly (1 shallow cut per 3 cm) — this helps prevent curling while cooking and ensures even contact with the pan for a crisp finish.

Heat a heavy, ovenproof skillet (cast-iron preferred) over medium-high heat until shimmering. Add 1/2 tbsp (7–8 ml) of the olive oil and swirl to coat. Place the salmon fillets skin-side down (if present) and press gently for 8–10 seconds to ensure full contact so the skin crisps evenly. Sear without moving for 2–3 minutes until the skin is deeply golden and releases easily from the pan. High heat gives a quick Maillard reaction — that brown crust adds savory flavor and texture.

Flip the fillets and spoon a little of the remaining olive oil over the top, then transfer the skillet to the preheated oven. Roast for 4–7 minutes depending on thickness (about 6–7 minutes for a typical 2–2.5 cm / 3/4–1-inch fillet). Aim for an internal temperature of 52–55°C (125–130°F) for medium, remembering there will be a couple degrees of carryover heat while resting. Finishing in the oven cooks the center gently so the salmon remains moist.

Drain the cooked sweet potatoes well, then return them to the hot pot off the heat for 30–60 seconds to let excess steam evaporate — this step prevents watery mash. Mash the potatoes with the remaining 1/2 tbsp olive oil, the zest of half a lemon, 1–1½ teaspoons salt (adjust to taste), and several grinds of black pepper. For an extra-silky texture, whisk in 1 tablespoon of warm water or a splash of milk if desired and whip briefly with a fork or hand-masher — the oil and minimal liquid keep the mash glossy without making it heavy.

Blanch the green beans: bring a small pot of salted water to a boil, drop in the trimmed 200 g green beans, and cook for 2–3 minutes until bright green and just tender. Immediately transfer them to a bowl of ice water to stop cooking and preserve color and snap. Blanching removes raw edge and shortens the final sauté time so beans remain vibrant.

Heat a medium skillet over medium heat and add the 2 teaspoons butter. When the butter foams, add the smashed garlic clove (if using) and cook briefly until fragrant (20–30 seconds) to flavor the butter — don’t brown it. Add the blanched green beans, toss to coat, and cook 1–2 minutes until warmed through and glossy. Remove the garlic, if you like, to avoid strong raw garlic bites. Season with salt, pepper, and a squeeze of lemon juice to brighten.

When the salmon comes out of the oven, transfer to a plate and let it rest for 2–3 minutes. Resting allows juices to redistribute; cutting immediately would cause moisture loss. Taste the mash and adjust seasoning; stir in half of the chopped dill or parsley for freshness.

To plate: spoon a generous dollop of sweet potato mash onto each plate, place the salmon fillet on top (skin-side up if crisp), arrange the sautéed green beans alongside, sprinkle with the remaining fresh herbs, and serve with lemon wedges. A final squeeze of lemon over the salmon brightens the dish and balances the richness.

Optional finishing touch: drizzle a teaspoon of good-quality olive oil or a few drops of lemon-infused olive oil over the salmon to add aroma and sheen just before serving.