Preheat the oven to 180C/350F/Gas 4.
For the tarte tatin, heat the sugar in a small ovenproof frying pan over a low heat until melted.
Add the butter and heat until the mixture is caramel coloured.
Add the apricot halves cut-side up, scatter with the sultanas and cook gently for 2-3 minutes, or until softened.
Roll the pastry out on a lightly floured surface to the thickness of a one pound coin.
Cut out a circle of pastry the same size as the circumference of the frying pan. Place the pastry on top of the apricots and press down around the edges to seal in the filling.
Transfer to the oven and bake for 12-15 minutes, or until the pastry is golden-brown on top. Remove from the oven and leave to cool slightly.
Slide a palette knife around the edge of the tart, then carefully turn out onto a serving plate.
For the almond brittle, place the sugar into a non-stick frying pan and heat gently. When the sugar has melted and is beginning to turn a caramel colour, add the almonds and stir well to coat them all.
Pour onto a non-stick mat or baking sheet and leave to cool. When cool, break into pieces.
To serve, cut the tarte tatin into generous wedges and place onto serving plates with a scoop of ice cream and a sprinkling of almond brittle.