Preheat oven to 200°C/180°C fan-forced. Grease a 20cm x 30cm slice pan and line base and 2 long sides with baking paper, extending paper 5cm over edges.
Arrange vegetables in pan in a single layer. Whisk eggs and cream in a large bowl until smooth and combined. Add grated cheese and season to taste. Whisk to combine. Pour over vegetables. Mix the onion jam and mustard in a small bowl. Dollop over vegetables. Arrange soft-rind cheese on top, slightly pushing into egg mixture. Bake for 40-45 minutes, until golden and set. Stand in pan on a wire rack for 20 minutes to cool slightly.
Serve warm or at room temperature scattered with rocket leaves.
