Preheat oven to 400°F (200°C).
In a large saucepan, melt butter over medium heat. Cook onion, garlic, vegetables and fennel seeds for 3 to 5 minutes or until onions and garlic are golden. Salt and pepper to taste and transfer to an ovenproof dish.
In a bowl, combine cheese, melted butter, breadcrumbs and parsley. Salt and pepper to taste.
Top vegetables evenly with cheese mixture. Bake 15 minutes or until vegetables are soft and cheese topping is golden and crusty.
Note: The croustade may be prepared ahead and baked or reheated just before serving.