1.Heat butter and oil in a frying pan; cook garlic, stirring, over a very low heat, for 10 minutes or until soft and browned lightly. Remove from pan.
2.Add leek to the same pan; cook, stirring, until soft. Add sugar; cook, stirring occasionally, for about 15 minutes or until mixture caramelises.
3.Preheat the oven to hot, 220°C.
4.Cut rounds from pastry sheet using 4.5cm cutter. Place rounds on greased oven tray and put another greased oven tray on top. (This cooks pastry through while stopping it from rising.) Bake rounds in a hot oven for 10 minutes or until browned lightly. Remove the top oven tray.
5.Divide cheese among pastry rounds; top with caramelised leek and piece of garlic. Return tarts to oven for further 5 minutes or until cheese is soft. Serve warm.
This recipe makes 24 tartlets. The pastry rounds can be made a day ahead; the garlic and leek mixture can be made up to 8 hours ahead. Top pastry rounds and reheat just before serving. Not suitable to freeze. Not suitable to microwave.Note