Use your clean hands to scrunch the minced beef with half the pesto and a pinch of sea salt and black pepper. Split into 12 pieces and, with wet hands, roll into balls. Brown the balls all over in a non-stick frying pan on a high heat with 1 tablespoon of olive oil, shaking the pan regularly.
Once the balls are golden and gnarly, pour in the tomatoes, breaking them up with a wooden spoon, along with just a quarter of a tin’s worth of water. Bring to the boil, slice the mozzarella and lay over the balls, pop the lid on and leave to thicken for 5 minutes on a medium heat. Meanwhile, warm your buns in a large dry non-stick frying pan or in the oven on a low heat.
Split each bun and spread 1 heaped teaspoon of pesto inside. Divvy up the balls and mozzarella with a little sauce, serving the rest on the side for dunking.