2) Heat the extra-virgin olive oil in a large frying pan over a medium heat, add the anchovies and stir into the oil until melted. Add the garlic, turn the heat to low and saute for a couple of minutes. Stir in the tomatoes, crushing them up, then stir in the stock. Season with a little black pepper, add the capers and olives and simmer for a few minutes.
3) While the sauce simmers, cut the tuna into chunks and grind in a food processor into a coarse mixture. Mix in the egg, breadcrumbs and parsley and season with a little salt and black pepper. Remove the tuna mixture from the processor to a bowl and add a drizzle of olive oil. Stir to combine; adding the oil will prevent mixture from sticking to your hands as you roll the balls.
4) Roll the tuna into small balls and drop these into the sauce. Cover the pan and simmer the tuna balls in the sauce, about 4 to 5 minutes.
5) Place the pasta into a serving bowl. Add the tuna and sauce, toss to coat and garnish with shredded basil.