Heat oil in a wok or a frying pan over medium heat. Add the curry powder, onion and pork, season and cook for about 10 minutes. The pork should be just cooked. The juices should have evaporated from the pan. Toss in the peas and potatoes. Remove the pan from the heat, add the chopped herbs and set aside to cool.
Lay the filo pastry sheets in a stack on a clean board. Cut into quarters to give 4 rectangles from each sheet. Cover the pastry with a barely damp tea towel to prevent drying out.
Lay one sheet of filo on the work surface with a short side nearest to you. Place a dessertspoonful of this filling on the end nearest you and fold the bottom left corner of the pastry over to meet the right-hand side and enclose the filling in a triangle. Continue folding the parcel over down the length of the pastry to create a neat triangle parcel. Brush the loose edge with a little of the beaten egg to seal, then place on a baking sheet.
Repeat to make 20 samosas, then brush them with beaten egg and chill until ready to cook.
Preheat the oven to 220°C (425°F). Lightly spray the samosas with cooking oil spray and cook for 10-14 minutes in the oven until golden brown. Serve hot with mint and yoghurt chutney.