David Tanis’ Pakistani potato samosas

For the dough:

300g plain flour

½ tsp salt

1 tsp ajwain or cumin seeds

50ml vegetable oil

110ml cold water

For the filling:

700g russet potatoes, peeled, in 1-inch cubes

3 carrots, chopped, optional

2 ½ tbsp vegetable oil, plus about 3 cups more for frying

1 onion, chopped

salt

pepper

1 tsp cumin seeds

1 tsp black mustard seeds

1 tsp grated garlic

1 tsp grated ginger

2 Serrano chillies, finely chopped

1 tsp turmeric

½ tsp garam masala

2 ½ tbsp lemon juice

1 handful chopped coriander, tender stems and leaves