Stir the mascarpone, Parmesan and egg yolk together in a bowl with a large pinch of salt and a few grinds of black pepper.

In another bowl, stir together oil, herbs and shallot.

Roll out pie crusts large enough to make 8 - 4 inch rounds. Place rounds on silicone baking sheet.

Drop a level tablespoon of the cheese mixture onto the center of each, spreading just enough to leave a 1/4-inch border.

Arrange the tomatoes on top of the cheese in the center of the tarts (about 6 halves per tart), leaving about a 1/4-inch cheese border. Fold and crimp the edges of the crust just over the cheese but leaving the tomatoes uncovered.

Sprinkle about tsp of herb oil/shallot mix over each.

Bake until the crust is golden brown and the tomatoes are wilted and lightly browned in spots, 20 to 25 minutes. Serve warm or at room temperature.