Heat the oven to 200°C/180°C fan/ gas 6. Put the cherry tomatoes on a baking tray, drizzle with a little oil and season. Roast for 20 minutes until softened and turning sticky.
Meanwhile, unroll the pastry. Trim and discard 5cm off the uneven end from the centre of the coil. Cut into 4 rectangles and transfer to a baking sheet. Lightly score a border 1cm from the edge of each rectangle and prick the middles with a fork.
Bake for 8 minutes until puffed up and just starting to turn golden. Press the centres of the rectangles down with your fingers, leaving the border raised higher.
Meanwhile, in a small mixing bowl mix the cream cheese, 1 egg yolk, parmesan and chives, season and divide among the tarts. Top with the tomatoes, then lightly beat the other yolk and brush over the pastry borders. Bake for 10-12 minutes until the pastry is puffed and golden. Serve drizzled with oil and scattered with fresh basil leaves.