Heat 2 tablespoons oil in a wok. Fry curry leaves, potatoes and onion till fragrant. Add tuna and stir in seasoning to mix. Fry until mixture is dry. Add red chilli and sprinkle in cornflour to bind the mixture well. Dish out and put aside to cool.
To prepare water dough: Sift flour into a mixing bowl. Add in the rest of the ingredients and knead into a smooth dough. Cover dough with a damp tea towel and leave aside to rest for 25 minutes.
To prepare oil dough: Combine all ingredients together and mix into a soft dough. Divide the dough into equal portions.
Divide water dough into the same number of portions as the oil dough. Roll out each portion into a large round piece and place a portion of oil dough in the centre. Wrap water dough completely around the oil dough. Roll out into an oval then into a swiss roll. Do this again one more time. Next, roll out into a rectangle and cut each portion into 2 equal circles with a fluted cutter.
Spoon 1 tablespoon filling into the centre of a pastry round. Top with the other pastry round. Dip a fork in flour and press down the edges to secure. Repeat until all ingredients are used up.
Heat oil in a wok and deep fry the puffs over medium heat until golden brown and crispy. Drain the puffs well and serve immediately.