Put the mince in a mixing bowl with the pesto and basil and mash together with a fork to blend the pesto and herbs into the mince. Shape the mince into 24–30 small balls.
Heat 1 tablespoon of the oil in a large, heavy-based frying pan and cook the chicken balls over a high heat, shaking the pan occasionally to turn the meatballs, for 15 minutes or until golden brown and cooked through.
Meanwhile, heat the remaining oil in a separate frying pan and cook the onion over a moderately high heat for 3–4 minutes, stirring until softened. Add the chopped tomatoes and tomato purée and season generously with salt and pepper. Bring to the boil, then reduce the heat and simmer, uncovered, for 5 minutes or until the sauce has reduced and thickened slightly.
Stir the meatballs into the tomato sauce and serve with fresh pasta shapes, if liked.