Preheat oven to 375°F (190°C) or BBQ to medium.
Place leeks and potatoes on a baking sheet, coat with oil and season.
Bake for 20 to 25 minutes or until roasted and tender. On the BBQ, cook over indirect heat until vegetables are grilled and tender.
Let stand at room temperature.
Cut leeks into chunks and sweet potato wedges in half. Set aside.
Drizzle lime juice over fish cubes and sprinkle with grated ginger.
Marinate for 10 minutes in the refrigerator for a rawer ceviche or up to 60 minutes for a more cooked fish.
Gently mix leek, potatoes, corn, jalapeño and cucumber. Drizzle with lime juice and a dash of olive oil, then adjust the seasoning.
Place the salsa on a plate, add the fish and sprinkle with quinoa, radishes and cilantro. Serve with corn chips or croutons.