Preheat the oven to 180°C.
Heat olive oil in a pan and sauté the onion until soft.
Stir in the chopped tomato and tomato purée and cook for five minutes.
Add basil and stock, then blend with a stick blender until smooth.
Mix beef mince, beaten egg, tomato purée, and garlic in a bowl.
Shape the mixture into 4cm meatballs.
Fry the meatballs in vegetable oil until golden-brown on all sides.
Simmer meatballs in the tomato sauce for ten minutes until cooked through.
Brush tortillas with oil and fry in a pan until crisp.
Fill the crispy tortillas with meatballs and sauce to serve.