Sift flour and salt into a mixing bowl. Toss cubed butter into flour and work with your fingertips until mixture resembles fine breadcrumbs. Add ice-cold water to combine well.
Transfer dough onto a lightly floured board and knead until smooth. Wrap tightly with greaseproof paper or cling film and refrigerate for 30 minutes.
Roll pastry into a 30cm x 15cm rectangle. Fold over one-third of the pastry, lightly dust with flour and fold remaining third of the pastry over the first fold. Refrigerate for 15 minutes. Repeat the rolling-folding-chilling process two more times.
Folding: Cut pastry into two equal parts and roll out each piece into a 15cm x 20cm rectangle. Place one piece of pastry on a lightly greased tray. Spread filling over, leaving a border of 2cm all round.
Fold the other piece of pastry into half and cut through the folded edge at 1cm intervals.
Carefully unfold pastry B and place over the filling. Press the edges of the pastry together with your forefinger to seal.
Brush jalousie with egg glaze and bake in a preheated oven at 200ºC for 30 minutes or until pastry is puffed and nicely browned.
To make filling: Heat 2 tbsp oil in a saucepan, fry onions and garlic till soft. Add in curry leaves and the rest of the vegetables and seasoning ingredients. Stir-fry well. Dish out and leave aside to cool.