In a frying pan heat 2 tbsp of the oil (a medium heat). Throw in the onion and cook until softened. Stir in the corn, garam masala, lime juice put the feta in right at the end and cook for 1 min until any liquid evaporates. Leave to cool.
Take a sheet of filo and cut in half length ways. Brush gently with some of the remaining oil.
Spoon 2 tbsp of sweetcorn mixture on top of each half. Fold each over into a triangle. Repeat with the remaining filo sheet.
Put the cornflour in a small bowl and add enough water to make a thin paste. Brush the paste over the triangle edges so the seals are secure. Sprinkle with cumin seeds.
Put the samosas on a baking tray. To cook straight away, brush tops with reserved oil. Bake for 15 mins until golden and crisp.
