1.Place the flour, icing sugar and cold butter in a food processor and process until combined. Add egg and process until just combined. Turn out onto a floured bench and knead gently into a soft dough. Wrap the pastry in plastic wrap and refrigerate for 30 minutes.
2.Lightly grease a 23cm round loose-base flan tin. Roll pastry out on a lightly floured surface (or between 2 sheets of baking paper) until large enough to line the tin, about 3mm thick. Use a rolling pin to lift the pastry into the tin; press into side.
3.Trim the edge and prick the pastry with a fork over the base. Refrigerate for 30 minutes.
4.Preheat oven to 200°C (180°C fan-forced). Line pastry with baking paper and cover with uncooked rice or beans (or pastry weights) to weigh the paper down; place tin on an oven tray. Bake for 15 minutes, then remove the paper and weights, and bake for a further 10 minutes or until browned lightly. Cool.
5.Meanwhile, place the nuts and sesame seeds on an oven tray. Roast in oven for about 8 minutes or until fragrant and browned lightly. Reserve 1 /3 cup of nuts and seeds for decoration.
6.Combine the condensed milk, butter and golden syrup in a medium saucepan; stir over a medium heat until boiling. Stirring constantly, cook over medium heat for about 10 minutes or until mixture is thick and a caramel colour.
7.Working quickly, combine the hot caramel, remaining warm nuts and seeds in pan; spread mixture into the pastry shell. Decorate top of tart with reserved nuts and seeds.
8.To serve, cut with a sharp knife heated with hot water and cleaned after each cut.