Wrap the salmon fillets in little parcels of foil, rubbed with oil to prevent the fish sticking. Preheat the oven to 350° F. Meanwhile, boil sweet potato chunks in plenty of salted water until soft. Roast the salmon parcels for up to 20 minutes, but check them often to make sure they don’t overcook and sink into chalky dryness. For the last 5 minutes or so of the salmon’s cooking time, put the kale—rubbed with olive oil and seasoned with plenty of sea salt flakes—on a separate tray into the oven to crisp and sizzle. Mash the sweet potato with butter, salt, and—Åsa’s secret ingredient—an extravagant drizzle of heavy cream.