First, prepare the meatballs. Using your hands, divide and shape 12 meatballs.
Wash your hands and keep the meatballs covered in the fridges until ready to cook them.
Preheat a wide sauté pan, over medium high heat and drizzle some oil in the pan. Add the meatballs and season with salt and pepper. Sear the meatballs for 2-3 minutes until coloured on all sides.
Add the chopped carrot, onion, garlic and mushrooms. Continue to sear for a further 2-3 minutes until the vegetables start to colour too.
Add the tomato sauce and extra water. Sprinkle the herbs, check the seasoning and bring to simmer. Simmer with a lid on for 3-8 more minutes to ensure the meatballs are nearly cooked through. ( if preparing in advance, fully cook the meatballs, if you will place the meatballs in the oven in for the next step then you can remove then after 3-4 minutes as they will be baking a further 15 minutes in the oven.)
Once ready, remove from the heat. Transfer in a ceramic or baking dish. And keep aside.
Brush the pesto generously over each filo pastry sheet and add the next one over to create a few layers of filo pastry.
Line over the meatballs. Sprinkle with salt and pepper and place in the oven for 15-20 minutes until the filo pastry is golden brown and crispy and the meatballs are fully cooked.
Remove from the oven and enjoy immediately.