1.Make pastry. Process flour, sugar and butter until coarse. Add egg yolk, process until combined. Knead on floured surface until smooth. Roll pastry between sheets of baking paper to 4mm thickness. Refrigerate 15 minutes.
2.Grease six-hole (¾-cup/180ml) texas muffin pan. Cut six 11cm rounds from pastry. Press rounds into pan holes, prick bases all over with fork. Refrigerate 30 minutes.
3.Preheat oven to 160°C (140°C fan-forced).
4.Combine cream and milk in small saucepan. Split vanilla bean in half lengthways, scrape seeds into pan (reserve pod for another use). Bring to the boil. Beat egg yolks and sugar in small bowl with electric mixer until thick and creamy. Gradually whisk hot cream mixture into egg mixture. Pour warm custard into pastry cases.
5.Bake about 30 minutes or until set, cool 15 minutes. Refrigerate 1 hour.
6.Meanwhile, make praline, combine sugar and the water in small saucepan, stir over heat until sugar dissolves. Boil, uncovered, without stirring, about 8 minutes or until golden in colour. Place nuts, in single layer, on greased oven tray. Pour toffee over nuts, stand about 15 minutes or until set. Break toffee into large pieces, process until chopped finely.
7.Preheat grill. Remove tarts from pan, place on oven tray. Sprinkle custard with praline, grill until praline caramelises. Serve immediately.
If pastry is too dry, add 2 teaspoons of water with egg yolk.Note