1. Preheat oven to 180°C (350°F).
2. Heat margarine in a saucepan over medium-high heat. Add zucchini and fry 2 minutes, until golden.
3. Add flour, whisking constantly. Heat 1 to 2 minutes, stirring all the time.
4. Whisk in milk. Continue to stir to prevent lumps from forming. Cook over medium-high heat until thick, about 7 to 8 minutes. Season to taste.
5. Add crab flakes and salmon, along with corn. Simmer over low heat, stirring occasionally, for about 5 minutes.
6. In the meantime, place vol-au-vent pastries on a baking sheet in oven and bake for 5 minutes or until hot.
7. To serve, spoon sauce over pastries, sprinkle with fresh chives and serve with broccoli florets.
To reduce the saltiness of the crab flakes, soak in a large bowl of cold water for about 15 minutes.
Variation: Replace the salmon or pollock by frozen shrimp.