Beat 1 egg and 100g sunflower margarine together. Add the flour and rub together until well mixed. If too dry, add a tablespoon of water. Turn out onto floured board and knead until smooth. Chill for 30 minutes.
Heat oil in saucepan and add in carrots, leeks and seeds. Turn down head and allow to sweat for 15 minutes. When soft, turn off heat and set aside. Remove pastry from fridge and allow to come to room temperature.
Roll out and line a greased ceramic pie dish with pastry. Prick with a fork. Beat the remaining 3 eggs in a bowl. Add the carrot and leek mixture. Season with salt and black pepper. Pour the mixture into pie dish.
Bake in preheated oven for 35 minutes or until mix is cooked through. Test by sticking a knife blade into centre of pie, if it comes out wet then allow to cook for wee bit longer.