Stem and rinse berries. Crush 1/4 of the gooseberries in the bottom of a saucepan. Combine sugar, cornflour and salt; mix with crushed gooseberries. Cook and stir until mixture boils. Cook further 2 minutes. Remove from heat, and add in remaining whole gooseberries.
Pour fruit filling into lined pastry case. Adjust top pastry, pinching the seams together to seal and cut slits to let steam escape. Brush with milk and sprinkle over sugar.
Bake in preheated oven for 35 minutes or until pastry is golden in colour.