Pre-heat the oven to 200 °C, 400F, Gas Mark 6. Place the salmon on a baking sheet and sprinkle the Cajun Seasoning over both sides. Bake for 15-20 minutes

Meanwhile, place the sweet potato in a large pan of boiling salted water and cook until tender. Drain. Mash well and stir in the Creme Fraiche and Cajun Seasoning. Blanch the leeks until softened and drain.

Place the sweet potato on the plate, scatter over the leeks and top with the salmon.