Put the onions and 2 tbsp oil in your biggest frying pan, and fry gently until softened. Add the garlic, then increase the heat and fry for a few minutes. Scoop half the softened onions from the pan into a large mixing bowl.
Add the bay leaves, tomatoes, passata, purée, brown sugar and red wine vinegar to the frying pan, and bring to a simmer. Bubble for 20 minutes until the sauce has reduced and thickened, and the surface is glistening. Season.
When the reserved onions have cooled, add the beef mince, breadcrumbs, fennel seeds, oregano and egg with plenty of seasoning. Mix everything with your hands really well, then shape into 20 meatballs. Heat 1tbsp oil in a non-stick frying pan and brown the meatballs in batches, adding more oil as you need – the meatballs should be almost cooked through. Cool. Mix 200g of the grated mozzarella with the mascarpone and a little salt.
When everything has cooled to room temperature, combine the meatballs and tomato sauce in a big baking dish. Blob over the cheesy mascarpone, and scatter over the remaining mozzarella. Freeze now.
Heat the oven to 180C/fan 160C/gas 4. Cover the dish tightly with an extra layer of foil and bake for 30 minutes, then remove the foil and bake for a further 30-45 minutes, until the meatballs are piping hot and cooked through, and the cheesy top is golden and bubbling. Let the dish cool for 5 minutes, then add a drizzle of olive oil and a scatter of fresh oregano, if you like, before spooning straight from the dish. Serve with crusty bread, pasta or rice.
*Freezing notes: Open-freeze in the baking dish until solid, but don’t leave it for too long, then cover with a layer of foil, then clingfilm to keep airtight (use clingfilm on its own and you risk taking off the cheesy topping when you remove it), or freeze in individual baking dishes in the same way. The day before you want to bake them, transfer the frozen dish to the fridge. When defrosted, finish the dish as above.
Source: Pinterest / Olive Magazine
Photo Credit: Pinterest/ Olive Magazine