Mix the lemon zest, breadcrumbs and milk together and set aside. Mix in the mozzarella, pesto, chicken, most of the basil leaves and half the garlic. Season well with salt and pepper and mix together using your hands until evenly combined. Roll into 20 balls, around 35g, the size of ping pong balls. Heat the olive oil in a pan over a medium-high heat. Add the meatballs and give them a shake to coat in oil. Fry for 6-8 mins until browned all over. Remove to a plate.

Tip the onion into the pan along with a pinch of salt, and stir to coat. Cook for 8-10 mins until beginning to soften, then stir in the remaining garlic and chopped basil stems. Cook for 2-3 mins until fragrant. Tip in the can of tomatoes, then swill out the can with a good splash of water. Add that to the pan, then stir in the sugar and some seasoning. Bring to a simmer, then nestle the meatballs into the sauce.

Cook for 15 mins until reduced and the meatballs are cooked through. Season to taste again if needed and add a squeeze of lemon juice, if you like. Spoon over the pasta and sprinkle over the remaining basil leaves to serve.