Heat oven to 180C/fan160C/gas 4. Roll out the pastry on a lightly floured surface, then use it to line a 23cm loose-bottom tart tin. Line with non-stick baking parchment and baking beans, then bake for 15 mins. Remove the beans, then cook for 10 mins more until golden. Remove from the oven, then reduce the heat to 140C/fan 120C/gas 1.
While the case is cooking, heat the butter and brown sugar in a shallow pan. When the sugar has completely dissolved, throw in the gooseberries and toss in the caramel. Cook for a few mins until they start to split, but before they have burst completely. Remove from heat and leave to cool. Once cool give them a stir, then tip into pastry case.
For the meringue topping, whisk the egg whites to soft peaks. Whisk in the caster sugar a spoonful at a time, then whisk in
the cornflour. Carefully blob the meringue over the gooseberries and gently spread to cover. Bake for about 40 mins until the meringue is cooked and lightly browned.