1.Place both sheets of pastry on a large, baking paper-lined oven tray. Join them together by slightly overlapping the pieces of pastry and pressing them together. Roll the sides of the pastry over and mark with a fork to give a decorative edge. Refrigerate for 30 minutes.
2.Meanwhile, heat the oil in a large, heavy-based frying pan. Stir in the onion; cook, covered, over a low heat, for about 20 minutes, scraping the base of the pan every few minutes to ensure it doesn’t catch. Add the garlic, thyme, rosemary, sugar and vinegar; cook, stirring, for a further 10 minutes until the onion is golden and caramelised. Remove from the heat; stir in the parsley.
3.Preheat the oven to 200°C (180°C fan-forced).
4.Cover the pastry with a second sheet of baking paper; top with a second baking tray as a weight. Bake for 10 minutes. Remove top tray and baking paper. Return pastry to the oven for a further 5 minutes or until crisp and golden. Spread the onion mixture over the pastry. Arrange the anchovies and olives over the top; return to the oven for a further 20 minutes or until pastry is browned and crisp.
5.Serve tart with a sprinkle of fresh basil leaves.
Not suitable to freeze or microwave.Note