Use any combination of large and cherry tomatoes for these tarts. Roasting the tomatoes first reduces their water content and makes it easier to get a crisp base on the tarts. For a vegetarian option, simply leave out the prosciutto.
1½ kilograms tomatoes
¼ cup olive oil
2 tablespoons balsamic vinegar
2 tablespoons brown sugar
1 clove garlic, crushed
1 tablespoon chopped thyme or rosemary
sea salt and freshly ground pepper
4 sheets ready-rolled puff pastry
1 egg, lightly beaten (egg wash)
1 tablespoon raw sesame seeds
3 tablespoons sour cream
1 tablespoon Dijon mustard
1 cup grated Gruyère or Cheddar cheese
20 large kalamata olives, pitted
4 slices prosciutto or 8 very thin slices salami
Preheat the oven to 200˚C. Cut the larger tomatoes into big chunks and place in a large bowl with the whole cherry tomatoes. Add the olive oil, vinegar, sugar, garlic and thyme, season well and toss to coat. Spread the tomatoes in a single layer on a large lined baking tray, scraping over all the oil from the bowl. Roast for 20 minutes.
Using a slotted spoon, carefully transfer the tomatoes to a cake cooling rack set over a tray and set aside to cool. The tomatoes will be soft. Place the baking tray with all the tomato juices back in the oven and cook until they are reduced and syrupy, taking care they don’t catch and burn. Tip into a small bowl and reserve.
Cut a 20 cm circle from each sheet of pastry. Brush with egg wash and fold over a 2 cm border all the way around, pressing it down firmly. Place the pastry on a lined baking sheet. You may have to use two baking sheets. Brush the border with egg wash and sprinkle with sesame seeds. Combine the sour cream and mustard and spread over the base of the tarts. Sprinkle with the cheese then refrigerate until the pastry is firm.
Divide the roasted tomatoes and olives between the pastry cases and drizzle with the syrupy cooking juices. Bake for 20 minutes or until the pastry is golden and crisp. Let the tarts sit for at least 5 minutes then transfer to serving plates. Top with a slice of prosciutto or the salami and garnish with a few basil leaves.
The tomatoes can be roasted 2 days ahead. Refrigerate the cooking juices and tomatoes separately
The pastry can be prepared up to the point of spreading it with the sour cream and mustard. Cover with plastic wrap and refrigerate until ready to cook.